Parse pmOS tweaks yaml file

Would be nice to parse pmOS tweaks and offer these as well. We could:

• convert YAML to json when loading (see parse_yaml_to_json in flatpak-builder)
• use json-glib to parse it into objects
• map these to AdwPreferenceRows

Panel wise

This came out of a discussion with @Newbyte, @calebccff, @ollieparanoid and Martijm. If somebody wants to work on this let me know and I'm happy to provide some guidance.