Update to allow for dynamic maximum number of meeting songs

[sircharlo]

I'm away from my computer right now, but this line would need to be updated:

https://github.com/sircharlo/meeting-media-manager/blob/e6315e3d045d96a63eaf5b3189ecabc75aadf504/src/renderer/constants/general.ts#L49

Instead of a hardcoded 151, we should dynamically get the highest available sjjm track where the track number is less than 500 (the cutoff for songs with audio descriptions). The correct number is 158 as of today, but this is bound to change in the future.

[mtdvlpr]

@sircharlo, should have a fix ready now :)