Autosync Launchpad YAMLs to corresponding JSONs

[DaloLorn]

Attempt to autogenerate a branch description JSON whenever a branch description YAML is saved in an OpenSR mod repo. (Ditto for metadata JSONs from metadata YAMLs.)

• Toggleable in settings (and invokable as a new command, in case the user disables the automation!)
• Use the same filename casing as the source YAML, if possible. Otherwise, just use a standard pattern; no need to get fussy about it.
• Pretty much just parse the file as YAML and then stringify it to the other file as JSON if successful. Simple stuff; the hardest part is going to be detecting that the file got saved in the first place!