Tweak wording + Add badge w/ number of models on the hub

[julien-c]

it seemed pertinent to display this here but maybe we can also add it to some other places

[julien-c]

[Tooling comment] For some reason python utils/check_copies.py --fix_and_overwrite fails on my Python with following:

(.env) ipro:transformers gibbon$ python utils/check_copies.py --fix_and_overwrite
Traceback (most recent call last):
  File "utils/check_copies.py", line 432, in <module>
    check_model_table(args.fix_and_overwrite)
  File "utils/check_copies.py", line 414, in check_model_table
    new_table = get_model_table_from_auto_modules()
  File "utils/check_copies.py", line 328, in get_model_table_from_auto_modules
    spec = importlib.util.spec_from_file_location(
AttributeError: module 'importlib' has no attribute 'util'

[sgugger]

I think it's better at the top rather than the end of the list (I don't think a user will read to until the end of the list TBH). We could even put it further up the README!

[LysandreJik]

LGTM!