In the repo's root, install the dependencies (since we use yarn workspaces)
$ yarn
Before commiting, also build the modified actions, e.g.
/slack-notify-release $ yarn build
Then open a PR. Once it gets merged, make sure to bump the action's version, e.g.
/slack-notify-release $ yarn version --new-version minor
Lastly, force-refresh the v1 tag (since that's what the workflow targets).
Now push it.
$ git tag v1 -f
$ git push && git push --tags