Add Open Media Converter

[albilu]

Adds Open Media Converter (data/Open_Media_Converter) to the catalog.

Upstream repo: https://github.com/albilu/open-media-converter
AppImage (v0.0.1, x86_64): https://github.com/albilu/open-media-converter/releases/download/v0.0.1/Open_Media_Converter-0.0.1-x86_64.AppImage

Notes:

• Linked the release AppImage directly because the asset uses Open_Media_Converter naming while the repo slug is lowercase, so repo-URL autodetection may not match. Happy to switch to a repo link if the checker prefers it.
• The AppImage is self-contained (bundled JRE 23 + GTK 4, built with appimagetool) and ships an AppStream metainfo file plus desktop entry.
• Will submit an update PR for future releases as documented.

[albilu]

Note on the cancelled test run: I checked the job log (test run 35362035603). This is the repo's 10-minute job timeout firing, not a test failure:

• AppImage download (73MB), type-2 detection, FUSE mount and appdir-lint.sh all completed.
• worker.sh never exited non-zero; output stops after the lint/hint lines at 15:23:20 and the job was killed at 15:32:57 by timeout-minutes: 10 while the firejail launch/screenshot phase was still running (heavy Java/GTK app, slow screenshot automation).
• The Version=1.5 desktop-file note from the old validator is already fixed upstream (now Version=1.0); it will be in the next release. The PNG-icon warning is known.

Happy to refresh this entry (data/Open_Media_Converter) against a newer release if a re-run would help, or leave it for manual review.