docs: add next js with app router example (#7552)

* move the existing example to with-script-in-browser

* Add example with next js app router

* disable ssr for excalidraw client comp

* typo

* update output dir

* don't include nextjs example in tsconfig

* remove meta.json

* lint

* remove example.ts

* port

* move the examples outside packages and use the deps as workspaces in examples

* update gitignore

* fix example

* update path of build dir

* fix

* fix scripts

* try local path

* fix

* update commands

* fix

* fix

* fix script

* skip ts

* disable ts

* add vercel.json

* install

* update tsconfig

* fix lint

* remove console.log

* lets see if this works

* revert

* remove ts nocheck

* add types and some utils in nextjs example

* fix types

* updatw example and remove nextjs dynamic syntax so we don't import excal twice

* move both examples to workspaces and create generic example to be used by browser and next js both

* copy the static assets to nextjs

* fix ts config

* render custom menu items

* fix custom footer

* fix types in browser example

* use regular imports for importing excal and import it using dynamic next js in app router instead

* Add example for pages router

* fix css discrepancies

* fix css

* configure output dir

* fix

* fix css

* rename to with-nextjs

* move components to examples/excalidraw/components

examples/excalidraw/utils.ts

@@ -0,0 +1,146 @@
+import { unstable_batchedUpdates } from "react-dom";
+import { fileOpen as _fileOpen } from "browser-fs-access";
+import type { MIME_TYPES } from "@excalidraw/excalidraw";
+import { AbortError } from "../../packages/excalidraw/errors";
+
+type FILE_EXTENSION = Exclude<keyof typeof MIME_TYPES, "binary">;
+
+const INPUT_CHANGE_INTERVAL_MS = 500;
+
+export type ResolvablePromise<T> = Promise<T> & {
+  resolve: [T] extends [undefined] ? (value?: T) => void : (value: T) => void;
+  reject: (error: Error) => void;
+};
+export const resolvablePromise = <T>() => {
+  let resolve!: any;
+  let reject!: any;
+  const promise = new Promise((_resolve, _reject) => {
+    resolve = _resolve;
+    reject = _reject;
+  });
+  (promise as any).resolve = resolve;
+  (promise as any).reject = reject;
+  return promise as ResolvablePromise<T>;
+};
+
+export const distance2d = (x1: number, y1: number, x2: number, y2: number) => {
+  const xd = x2 - x1;
+  const yd = y2 - y1;
+  return Math.hypot(xd, yd);
+};
+
+export const fileOpen = <M extends boolean | undefined = false>(opts: {
+  extensions?: FILE_EXTENSION[];
+  description: string;
+  multiple?: M;
+}): Promise<M extends false | undefined ? File : File[]> => {
+  // an unsafe TS hack, alas not much we can do AFAIK
+  type RetType = M extends false | undefined ? File : File[];
+
+  const mimeTypes = opts.extensions?.reduce((mimeTypes, type) => {
+    mimeTypes.push(MIME_TYPES[type]);
+
+    return mimeTypes;
+  }, [] as string[]);
+
+  const extensions = opts.extensions?.reduce((acc, ext) => {
+    if (ext === "jpg") {
+      return acc.concat(".jpg", ".jpeg");
+    }
+    return acc.concat(`.${ext}`);
+  }, [] as string[]);
+
+  return _fileOpen({
+    description: opts.description,
+    extensions,
+    mimeTypes,
+    multiple: opts.multiple ?? false,
+    legacySetup: (resolve, reject, input) => {
+      const scheduleRejection = debounce(reject, INPUT_CHANGE_INTERVAL_MS);
+      const focusHandler = () => {
+        checkForFile();
+        document.addEventListener("keyup", scheduleRejection);
+        document.addEventListener("pointerup", scheduleRejection);
+        scheduleRejection();
+      };
+      const checkForFile = () => {
+        // this hack might not work when expecting multiple files
+        if (input.files?.length) {
+          const ret = opts.multiple ? [...input.files] : input.files[0];
+          resolve(ret as RetType);
+        }
+      };
+      requestAnimationFrame(() => {
+        window.addEventListener("focus", focusHandler);
+      });
+      const interval = window.setInterval(() => {
+        checkForFile();
+      }, INPUT_CHANGE_INTERVAL_MS);
+      return (rejectPromise) => {
+        clearInterval(interval);
+        scheduleRejection.cancel();
+        window.removeEventListener("focus", focusHandler);
+        document.removeEventListener("keyup", scheduleRejection);
+        document.removeEventListener("pointerup", scheduleRejection);
+        if (rejectPromise) {
+          // so that something is shown in console if we need to debug this
+          console.warn("Opening the file was canceled (legacy-fs).");
+          rejectPromise(new AbortError());
+        }
+      };
+    },
+  }) as Promise<RetType>;
+};
+
+export const debounce = <T extends any[]>(
+  fn: (...args: T) => void,
+  timeout: number,
+) => {
+  let handle = 0;
+  let lastArgs: T | null = null;
+  const ret = (...args: T) => {
+    lastArgs = args;
+    clearTimeout(handle);
+    handle = window.setTimeout(() => {
+      lastArgs = null;
+      fn(...args);
+    }, timeout);
+  };
+  ret.flush = () => {
+    clearTimeout(handle);
+    if (lastArgs) {
+      const _lastArgs = lastArgs;
+      lastArgs = null;
+      fn(..._lastArgs);
+    }
+  };
+  ret.cancel = () => {
+    lastArgs = null;
+    clearTimeout(handle);
+  };
+  return ret;
+};
+
+export const withBatchedUpdates = <
+  TFunction extends ((event: any) => void) | (() => void),
+>(
+  func: Parameters<TFunction>["length"] extends 0 | 1 ? TFunction : never,
+) =>
+  ((event) => {
+    unstable_batchedUpdates(func as TFunction, event);
+  }) as TFunction;
+
+/**
+ * barches React state updates and throttles the calls to a single call per
+ * animation frame
+ */
+export const withBatchedUpdatesThrottled = <
+  TFunction extends ((event: any) => void) | (() => void),
+>(
+  func: Parameters<TFunction>["length"] extends 0 | 1 ? TFunction : never,
+) => {
+  // @ts-ignore
+  return throttleRAF<Parameters<TFunction>>(((event) => {
+    unstable_batchedUpdates(func, event);
+  }) as TFunction);
+};