Have both <RATING> [0-100] and <FMPS_RATING>

Hi. In #152 (closed) we can see that for the tag RATING there are many conflicting values used (Vorvis): 0-1, 0-5, 0-100. You said "A lot of people have rated their entire library with Sayonara and so I don't want breaking changes. But I'll provide some option where you can specify your desired interval"

[the present 'de facto standard' as per https://en.wikipedia.org/wiki/Vorbis_comment and others https://github.com/quodlibet/quodlibet/issues/3533 , 'RATING 1-5 stars with 20,40,60,80,100 as the actual string values' ].

For just the case of users of Sayonara, changing 0-5 to 0-100 for can keep 'stars' the same: 0 is the same for 'old' and 'new' conversion; if the program sees a value of 5 or lower, it would use the 'old' conversion to stars; if the program sees a value of 10 (or 6) to 100, it would use the 'new' conversion [10 (or 6 to 10) = half a star, 20 = a star..., ] .
[with a notice in the wiki/cahngelog: 'up to version 1.7.0-stable4 the tag was written from 0 to 5, from now on, the tag is written from 0 to 100; the stars will keep showing as before, but if you want the tag to be correctly read by other programs, you may need to change your previously tagged RATING'. ]

The no-conflicts solution for Vorvis is to use the <FMPS_RATING> tag , which is always from 0 to 1 (0, 0.1, 0.2... 1) [ https://forum.audacityteam.org/viewtopic.php?f=20&t=106385&start=10#p385348 , [the original spec link is dead, but the tag is used like this by Amarok, Clementine, Tauon , Cantata, Rhythmbox, Banshee, gmusicbrowser ... ]

So, best for legacy and future would be having both tags, RATING [0-100] and <FMPS_RATING> , maybe with a setting to chose using only one, or writing to both tags for maximum compatibility.

Thx