feat: show a mid point for linear elements (#5534)

* feat: Add a mid point for linear elements

* fix tests

* show mid point only on hover

* hacky fix :(

* don't add mid points if present and only add outside editor

* improve styling and always show phantom point instead of just on hover

* fix tests

* fix

* only add polyfill for test

* add hover state for phantom point

* fix tests

* fix

* Add Array.at polyfill

* reuse `centerPoint()` helper

* reuse `distance2d`

* use `Point` type

Co-authored-by: dwelle <luzar.david@gmail.com>

src/polyfill.ts

@@ -0,0 +1,26 @@
+const polyfill = () => {
+  if (!Array.prototype.at) {
+    // Taken from https://github.com/tc39/proposal-relative-indexing-method#polyfill so that it works in tests
+    /* eslint-disable */
+    Object.defineProperty(Array.prototype, "at", {
+      value: function (n: number) {
+        // ToInteger() abstract op
+        n = Math.trunc(n) || 0;
+        // Allow negative indexing from the end
+        if (n < 0) {
+          n += this.length;
+        }
+        // OOB access is guaranteed to return undefined
+        if (n < 0 || n >= this.length) {
+          return undefined;
+        }
+        // Otherwise, this is just normal property access
+        return this[n];
+      },
+      writable: true,
+      enumerable: false,
+      configurable: true,
+    });
+  }
+};
+export default polyfill;