Explicit export

[Dreamsorcerer]

We get mypy errors because nothing is explicitly exported from this library.

e.g.

fuzzers/payload_url.py:22:6: error: Module "atheris" does not explicitly export
attribute "instrument_imports"  [attr-defined]
    with atheris.instrument_imports():
         ^~~~~~~~~~~~~~~~~~~~~~~~~~

This explicitly exports everything mentioned in the README, using __all__. The alternative export mechanism is to use as syntax on the imports, if the first method is not preferred for any reason.

[TheShiftedBit]

There are actually many more things intentionally exported than just the ones mentioned in the readme.

[Dreamsorcerer]

There are actually many more things intentionally exported than just the ones mentioned in the readme.

Do you want me to add everything in the file? Or feel free to just update it directly.