devel/muon: Update to 0.5.0

- Fetch source archive from homepage (formerly the source archive was
  fetched from sourcehut)
- Execute pkg-config (formerly libpkgconf was used)

Changelog
=========
- muon analyze now has an LSP mode
- pkg-config-exec backend added. muon now supports shelling out to pkg-config
  (or pkgconf)
- bump meson support to 1.7
- more builtin dependency handlers
- lots of bug fixes
