frescobaldi 2.0.10: GUI for Lilypond music typesetter …

Note: this formula depends on Platypus, so the pull request includes a Platypus commit (0bf7015). This is the same commit already referred to in #22607, so it's probably best to wait on this pull request till #22607 is merged.

This is a pull request for Frescobaldi. A couple of notes:
* There is a Pip package for Frescobaldi, but it doesn't work (no download is available!), and I don't think it ever did. So we're not duplicating Pip.
* This formula (optionally) installs a Mac OS launcher .app, so that the program can be launched either from the command line or from the Finder. I believe that, as with FontForge, this enhances usability without vitiating Homebrew's mission. (Also, making the launcher is in the [official Frescobaldi Mac installation instructions](https://github.com/wbsoft/frescobaldi/wiki/Frescobaldi-Mac-OS-X-install-guide), which I've tried to follow fairly closely for this formula.)