Update tagging guidelines for audio files (#404)

Author: OzGav

docs/music-providers/filesystem.md

@@ -81,6 +81,7 @@ In addition to the settings outlined above to configure the provider there are a
 ## Tagging Files 
 
 - It is very important that all of your audio files contain proper [ID3 tag](https://en.wikipedia.org/wiki/ID3) information. The more comprehensive the tagging the better the results will be when using MA. For this reason it is strongly recommended that all files are tagged with [MusicBrainz Picard](https://picard.musicbrainz.org). This will ensure consistency and completeness of the tags that MA needs to work best. Other programs such as [Mp3Tag](https://www.mp3tag.de/en/) are often also based on the Musicbrainz catalog and can work as well provided they include ISRC and all MBID tags
+- Tags must have mutiple items separated by a semicolon. In Picard this is an option in OPTIONS >> TAGS >> ID3. Also in that section ensure V2.3 is used to avoid problems
 - MA requires the Album Artist tag to be set. If you do not have that tag set then what happens to those tracks when the provider is scanned depends on the `Action when a track is missing the Albumartist ID3 tag` setting for the local provider
 - For multi-artist tracks it is important that the `ARTISTS` tag (as distinct from `ARTIST`) is set, which is semi-colon delimited list of the artists on the track. If this tag is not set MA will attempt to parse the artist names from the `ARTIST` tag but if unusual or non-English joining words or symbols are used then this process may fail 
 - Music Assistant puts you in control by fully trusting the ID3 tags you provide, only additional information is scraped from metadata providers