Problem: mapping.lua can silently drift from the ya2s/nonicons upstream
font. The existing CI check only runs on PRs/pushes and just fails
without any actionable follow-up.
Solution: add a daily scheduled workflow that generates mapping.lua from
upstream nonicon.json and opens (or updates) a PR via
peter-evans/create-pull-request. Reuses the same branch to avoid spam.
Closes#7
