Randomized offset for shorter fractional loop playback

[hburgund]

For loop fractions that are less than or equal to 1/2, it would provide more playback variation if the first possible loop fraction wasn't always used. In other words, if there was a possible offset in the start time of the fractional loop.

Proposed Strategy

• only apply to loop fractions of 1/2 or less because these are the only cases in which more than one full fractional loop can exist within the full loop length without overlap
• maybe even better, only apply to loop lengths specified in the config e.g. loopFractions: [1/8o, 1/16o, 4/8o, 5/8, 6/8, 1/1] whereby all loops with "o" suffix are allowed to have an offset. This approach, I suppose, would circumvent any need to programmatically determine if a loop fractions can be offset, so maybe easier? Also might be a pain for other loop calc stuff since we now have non-numbers!
• for each loop fraction available for offset, calculate possible starting places by incrementing the specified fraction length while remaining less than full-length - fraction-length.
  • for 4/8o, possible starting offsets are 0 or 1/2
  • for 1/8o, possible starting offsets are 0, 1/8, 1/4, 3/8, 1/2, 5/8, 3/4, 7/8
  • there would be 16 available for 1/16o
• randomly select which offset to apply and then put that slice of the speaker audio into the playback buffer

I imagine there are other ways to go about this, so lmk what you think. This one seemed the simplest to me; maybe not the most ultimate flexibility, but captures the basics.