CharCut: another character-based MT evaluation metric (#290)

* add charcut

* make style

* add charcut dependency

* fix doctest example

* update charcut to v1.1.1

No verbosity anymore

* fix doctest

* Update metrics/charcut_mt/requirements.txt

Co-authored-by: Leandro von Werra <lvwerra@users.noreply.github.com>

* Update setup.py

Co-authored-by: Leandro von Werra <lvwerra@users.noreply.github.com>

* Delete .gitattributes

* fix features: always working on strings as samples

* Merge remote-tracking branch 'upstream/main' into charcut

* add typing

* Delete tests.py

* Update charcut_mt.py

* make quality

Co-authored-by: Leandro von Werra <lvwerra@users.noreply.github.com>