Combined FLX/EXT/PRO/SUP angle

2 separate NN decoding FLX/EXT or PRO/SUP. FLX/EXT-nn should have zero output when PRO/SUP-nn, vice versa.

[x] Check IMU angle, how Roll/Pitch reacts to FLX/EXT, PRO/SUP and FLX/EXT+PRO/SUP
- New zeroing procedure
- w/ FLX/EXT + PRO/SUP. FLX/EXT turns from Pitch angle to Yaw angle as PRO/SUP activates
- May need to use 3-NN for all of the RPY angle
[ ] Check NN performance under FLX/EXT/PRO/SUP combined
- If the performance is good (equal to separate FLX/EXT, PRO/SUP), use combined NN for demo; if not, implement the above NN config

dymnz / sEMG