Adding MMM tokenizer

[Natooz]

Following #40

[codecov-commenter]

Codecov Report

Patch coverage: 92.21% and project coverage change: +0.23 🎉

Comparison is base (9ff6808) 88.72% compared to head (d17e9bc) 88.95%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #41      +/-   ##
==========================================
+ Coverage   88.72%   88.95%   +0.23%     
==========================================
  Files          26       27       +1     
  Lines        3344     3586     +242     
==========================================
+ Hits         2967     3190     +223     
- Misses        377      396      +19     

Impacted Files	Coverage Δ
miditok/__init__.py	100.00% <ø> (ø)
miditok/midi_tokenizer.py	85.92% <ø> (ø)
miditok/tokenizations/remi_plus.py	87.59% <ø> (ø)
tests/test_one_track.py	70.42% <ø> (ø)
miditok/tokenizations/mmm.py	92.08% <92.08%> (ø)
miditok/constants.py	100.00% <100.00%> (ø)
miditok/tokenizations/__init__.py	100.00% <100.00%> (ø)
tests/test_bpe.py	90.10% <100.00%> (ø)
tests/test_multitrack.py	71.01% <100.00%> (ø)

☔ View full report in Codecov by Sentry.
📢 Do you have feedback about the report comment? Let us know in this issue.