Add GitHub Actions to build extension as Assets when Release

[TzuWei]

Refer to the Installation section in REAME.md

- Manually download and locally load to your browser (WIP)

Expected to add GitHub Actions to run yarn build and pack the /build into hackbar_<version>.zip that attached to Release Assets.

So that users can directly download and use it in their browser without clone and build by themselves.

It's also convenient to publish extension (e.g. chrome web store) with the auto build.