feat: Add onPaste prop to customise clipboard paste event

[fabien0102]

Add onPasteFromClipboard props to @excalidraw/excalidraw.

Example

A simple example to add a custom element when the text "special" is pasted in the scene.

import React, { useCallback, useRef } from "react";
import Excalidraw from "@excalidraw/excalidraw";
import {
  ExcalidrawAPIRefValue,
  ExcalidrawProps,
} from "@excalidraw/excalidraw/types/types";

export const App = () => {
  const ref = useRef<ExcalidrawAPIRefValue>(null);
  const onPasteFromClipboard = useCallback<Required<ExcalidrawProps>["onPasteFromClipboard"]>(
    (data) => {
      if (ref.current?.ready && data.text === "special") {
        /* do something special */
        const prev = ref.current.getSceneElementsIncludingDeleted();
        ref.current.updateScene({elements: [...prev, /* my special element */]})

        return true; // Prevent default paste action
      }

      return false; // Do the default paste action
    },
    []
  );

  return <Excalidraw ref={ref} onPasteFromClipboard={onPasteFromClipboard} />;
};

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[ad1992]

Also can you update changelog and README_NEXT.md ?

[ad1992]

Thanks for the PR @fabien0102 🎉