Fully automated release

[stoically]

Scheduled GitHub Action that checks for a new stable riot-web release. If there's one, bump the version in the manifest and publish using the API:

• AMO via web-ext sign: https://extensionworkshop.com/documentation/develop/web-ext-command-reference/#commands
  • depends on: https://github.com/mozilla/addons-server/issues/9913

[stoically]

Unlikely to support this, since it's useful to have the final say on when/what to deploy (also from a security perspective).