Add IDs to elements (#236)

* Add IDs to elements

- Move round rect function within the renderer

* Generate IDs using nanoid

* If element ID does not exist, add the ID during restoration

src/element/newElement.ts

@@ -1,4 +1,5 @@
 import { randomSeed } from "../random";
+import nanoid from "nanoid";
 
 export function newElement(
   type: string,
@@ -14,6 +15,7 @@ export function newElement(
   height = 0
 ) {
   const element = {
+    id: nanoid(),
     type,
     x,
     y,