update flatpak filesystem permissions: from home -> xdg-config

[fpfcmsr]

tested on a clean install - Pied looks in .config/speech-dispatcher, creates a backup if it exists, and overwrites it. This makes it clear what permissions pied needs as opposed to the broad filesystem=home.

[Elleo]

That's brilliant, thank you! I'm away at the moment, but I'll give this a test when I'm home next week.

[fpfcmsr]

What are your thoughts on storing the backup configs within .config/speech-dispatcher? To my knowledge pied creates ./config/speech-dispatcher/speechd.conf and .config/speech-dispatcher/modules/piper.conf, which could probably be backup up individually in a speechd.conf.bak-$day-$month-$year file.
I was looking at the code and thinking it might be nice to have everything unified in one directory. If it's something you'd consider I could look into creating an mr for it. This would allow flatpak sandboxing from --filesystem=home to --filesystem=xdg-config/speech-dispatcher:create (creates it if it doesn't already exist) and be really clear about what files pied needs access to.

[Elleo]

That sounds good to me, I was probably being a bit overly cautious in backing up the entire directory; but I really didn't want to end up in a scenario where a user might end up with a broken config and no way to revert.

[fpfcmsr]

Got busy all of a sudden but finally got some time to try my hand at the file level backups. Let me know what you think - opened a separate PR for it.