* feat: expose variable window.EXCALIDRAW_ASSET_PATH to allow host define the path for excalidraw assets
No more __webpack_public_path__ needed explicitly in host and it will default to unpkg cdn if window.EXCALIDRAW_ASSET_PATH is not defined
* fix
* add public path
* add public path
* assign only when env not test
* read from package.json
* Append content hash to excalidraw-assets so cache bursting happens when version update
* update changelog and readme
* update