Migrate `worker.js` to `worker.mjs`

[JounQin]

Although the main entry could still be commonjs, the worker could be changed as pure ESM.

[yashtech00]

hey, if i will migrate .js to .mjs it will affect eslint-prettier-plugin.js , so i need to migrate that also from .js to .mjs

[JounQin]

@yashtech00 No, it won't be affected.

Although the main entry could still be commonjs, the worker could be changed as pure ESM.

Please read more carefully.