[Github Actions] Automatic publishing to AMO and Chrome Web Store

[Compile-Time]

Add a Github Action flow to publish release archives of the extension to AMO and Chrome Web Store.

TODO:

• Check if the publishing can be automated for Firefox
• Check if the publishing can be automated for Chrome
• Implement automatic publishing for AMO
• Implement automatic publishing for Chrome Web Store
• Decide if the action should be run automatically after the release action.

[Compile-Time]

CLI Publishing for Firefox is possible with the web-ext tool and using the --use-submission-api flag. However, this will probably require a switch away from the NPM script build, since I assume that web-ext will build the extension and then publish it to AMO.

[Compile-Time]

Example for uploading a Chrome extension automatically: https://l-u-k-e.medium.com/continuously-deploying-a-chrome-extension-e95eeb7cca81