Improved version of workflow automation

[IvanSavenko]

Changes:

• mod names and descriptions can now be translated via Weblate. Workflow will now iterate all submods and embed their name/description into english.json of root mod. For mods using description.md, descriptions are now moved to separate, per-language file that can be translated via Weblate. On weblate push, workflow will propagate descriptions back to corresponding mod.json.
• Workflow should now automatically detect new translations, meaning it is now possible for translators to add translations via Weblate web UI without figuring out how to add files and make a PR in Github
• mod.json that is part of release now receives all fields from mod repository - screenshots, download size, download url, stars count. Meaning we can migrate this functionality from mod repository and keep it in place
• (VCMI 1.8) support for tracking mod update date. Now generated mod.json contains date of last mod update, which launcher can use
• Workflow should now support chain-loading mod dependencies - if mod depends on mod A, but mod A also depends on B, then workflow will automatically install both mod A and B
• Directory tree traversal when locating submods is now unified, and should properly handle mixed case
• Blocked concurrent CI runs so workflow runs from 2 consequent PR merges won't conflict with each other

TODO:

• review migration of descriptions - make sure that existing descriptions won't be overwritten, and that propagation of description translated via weblate works as expected
• consider migrating html-based descriptions to markdown