Create Workflow for Automated Store Publishing

[GODrums]

Motivation

Implements tasks 1-3 of #302.

Description

This PR adds a new Github Actions workflow to automate the publishing flow to extension stores (Chrome + Firefox).
It uses Actions provided by Browser Actions. The workflow starts directly after a successful run of the release workflow.

Setup

A general explanation for the tokens can be found here. The workflow requires multiple repository secrets to be set up:

# Extension ids
CHROME_EXTENSION_ID=""
FIREFOX_EXTENSION_ID=""
# Chrome Web Store secrets
# How to get them: https://github.com/PlasmoHQ/chrome-webstore-api/blob/main/token.md
# Or: https://github.com/fregante/chrome-webstore-upload-keys
OAUTH_CLIENT_ID=""
OAUTH_CLIENT_SECRET=""
OAUTH_REFRESH_TOKEN=""
# Firefox Add-On Store secrets
# How to get them: https://addons.mozilla.org/en-US/developers/addon/api/key/
AUTH_API_ISSUER=""
AUTH_API_SECRET=""

[GODrums]

@Step7750
I reworked the publishing using the Github Actions by Browser Actions now. The workflow is now designed to run directly after the release workflow has succeeded and reuses its uploaded assets.

[Step7750]

I've added the necessary secrets, so we should be good to go with merging this and trying it out.