CI/CD: Implement weekly builds.

Brings over the functionality in https://github.com/FreeCAD/FreeCAD-Bundle
to build Linux AppImage, macOS .dmg, and Windows 7z releases.

This version also creates a tagged release for each build, creating an
archive of the weekly builds as well as the ability to easily tie each
build to a git commit.  This will make running 'git bisect' easy to
identify sources of regressions.

package/rattler-build/osx/dmg_settings.py

@@ -0,0 +1,12 @@
+# Ensure default values are set in defines if they are not already provided
+defines.setdefault('containing_folder', '.')
+defines.setdefault('app_name', 'FreeCAD.app')
+defines.setdefault('icon_path', 'Contents/Resources/freecad.icns')
+
+
+files = [f"{defines['containing_folder']}/{defines['app_name']}"]
+symlinks = {"Applications": "/Applications"}
+badge_icon = f"{defines['containing_folder']}/{defines['app_name']}/{defines['icon_path']}"
+window_rect = ((200, 200), (600, 400))
+icon_locations = {f"{defines['app_name']}": (180, 150), "Applications": (420, 150)}
+size = "4g"