use pep-420 implicit namespace package

[bollwyvl]

This removes the intermediate backports/__init__.py which would conflict with other pre-PEP-420 backports.* packages.

References:

• ClobberError installing backports.zstd conda-forge/backports.zstd-feedstock#5

[Rogdham]

Thank you for the PR! I will need some time to properly test this. With the holiday season coming up, I will try to do that and ship a new release by the end of the year.

[bollwyvl]

No hurry! Have a lovely holiday.

I think with a MSPV of 3.9 in this repo, we're well and out of any danger, as PEP-420 was adopted in CPython 3.3.

[Rogdham]

I have tested this with various combinations of installing other packages such as backports.tarfile, backports.functools_lru_cache, backports.httpmethod, backports.strenum.

Everything seems to still work 🎉

Thank you for the PR!