REPO: Add a better way to manually trigger render-deploy for specific course(s)

[JuhoErvasti]

Description

Currently if a workflow fails due to some issue (see 72f21b9) and the issue is later fixed the changes to materials are not automatically updated, which requires a manual update. Triggering a manual update is a bit cumbersome however, since it requires you to make a new change to the materials.

Possible solutions? (quickly thought of)

Quick and dirty: Add a text file to each course folder like manual_update.txt. Add that to the search paths in render-deploy. Would require to open each file and edit however.

Maybe a better solution, but harder to implement: Add a text file to . or maybe src, edit that with a delimited list of course codes that is then read and the given courses updated.