Add the ability to supply a series description for XMLTV

In the Plex provided EPG, TV shows are able to have descriptions (along with individual episodes). For example, here is a programme in the Plex EPG (don’t mind the actual content, the Plex EPG for NZ leaves a lot to be desired):

Meanwhile, there is no way for an XMLTV provider to supply this information, which means that the series descriptions don’t appear in the guide and when recorded, the TV show doesn’t have a description. For example here is a programme under an XMLTV guide:

My suggestion is that a new tag be added for XMLTV guides allowing them to supply this data by adding a custom tag (much like what was done for sports and sports teams), for example series-desc. That way we could add something like this to the XMLTV and have the series description appear:

<series-desc>
Join the 1 NEWS team as they wrap up the day's latest developments, both here and abroad.
</series-desc>