Flatsplode

**Full Changelog**: https://github.com/amancevice/flatsplode/compare/0.5.0...v0.6.0

Update build

Drop Python 3.6 and lower, add Python 3.11
**Full Changelog**: https://github.com/amancevice/flatsplode/compare/0.4.1...0.4.3

Use flit for build process instead of setuptools
Add entrypoint for command line usage

Add `__version__` attribute to module

Exploding items with empty lists (`'fizz': []`) results in a value of `None` for that key.

Example:

python
>>> from flatsplode import flatsplode
>>> list(flatsplode({
... 'id': '78e5b18c',
... 'attrs': [],
... 'keywords': [
... {'fizz': ['fizza', 'fizzb']},
... {'buzz': []}
... ]
... }))
>>> [
... {'id': '78e5b18c', 'attrs': None, 'keywords.fizz': 'fizza'},
... {'id': '78e5b18c', 'attrs': None, 'keywords.fizz': 'fizzb'},
... {'id': '78e5b18c', 'attrs': None, 'keywords.buzz': None},
... ]