Implement --pattern or --patterns-from options

[mahikeulbody]

It would be nice to add --pattern or --patterns-from options in addition to --exclude and --exclude-if-present options already implemented.

It would be easier to "migrate" to Vorta when one has a patterns-from file already set to use with borg.

Thanks for the nice work !

[Hofer-Julian]

According to https://borgbackup.readthedocs.io/en/stable/usage/create.html this is still experimental. Not sure if it makes sense to include it in Vorta yet...

[palto42]

I'm using the --pattern option since many month via borgmaticand had no issues. In my view it's much easier to use since it allows a mix of include/exclude which can avoid the usage of complex regular expressions (e.g. exclude some path except specific sub-folder).