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/excalidraw-app/index.tsx

@@ -1,3 +1,4 @@
+import polyfill from "../polyfill";
 import LanguageDetector from "i18next-browser-languagedetector";
 import { useCallback, useEffect, useRef, useState } from "react";
 import { trackEvent } from "../analytics";
@@ -83,6 +84,7 @@ import { jotaiStore, useAtomWithInitialValue } from "../jotai";
 import { reconcileElements } from "./collab/reconciliation";
 import { parseLibraryTokensFromUrl, useHandleLibrary } from "../data/library";
 
+polyfill();
 window.EXCALIDRAW_THROTTLE_RENDER = true;
 
 const isExcalidrawPlusSignedUser = document.cookie.includes(