Use a GResource XML file

[cjmayo]

Advantages:

• Gtk.Application loads menus and the shortcuts window definitions automatically.
• 5 files: menus, shortcuts, CSS and the two remaining pixmaps can be combined into one file that is less than half the size of the uncompressed menu file.

Disadvantages:

• Adds a dependency on glib-compile-resources, which is bundled with GLib in Homebrew and Gentoo Linux and already installed in the GitHub Actions VMs. It is available in a separate package on Debian/Ubuntu.
• If modifying any of the files during development the GResource file needs to be recreated. This can be done with either setup.py build or ./bin/resources.sh.

[codecov[bot]]

Codecov Report

Merging #220 (46a9a3e) into master (7d6cb43) will decrease coverage by 0.00%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #220      +/-   ##
==========================================
- Coverage   86.39%   86.38%   -0.01%     
==========================================
  Files          57       57              
  Lines       10812    10806       -6     
==========================================
- Hits         9341     9335       -6     
  Misses       1471     1471              

Impacted Files	Coverage Δ
fract4dgui/director.py	67.59% <ø> (-0.07%)	:arrow_down:
fract4dgui/application_window.py	88.51% <100.00%> (-0.31%)	:arrow_down:
fract4dgui/main_window.py	63.71% <100.00%> (+0.24%)	:arrow_up:

---

Continue to review full report at Codecov.

Legend - Click here to learn more Δ = absolute <relative> (impact), ø = not affected, ? = missing data Powered by Codecov. Last update 7d6cb43...46a9a3e. Read the comment docs.