Update package setup

[florimondmanca]

• Drop Python 3.6 support.
• Add official Python 3.11 support.
• Bump dev dependencies.
• Switch to pyproject.toml.
• Switch to Makefile scripts.
• Use newest CI templates.
• Update tests.

[codecov-commenter]

Codecov Report

Merging #55 (1c8f304) into master (9aa20b3) will decrease coverage by 0.31%.
The diff coverage is 100.00%.

❗ Current head 1c8f304 differs from pull request most recent head f03f1c7. Consider uploading reports for the commit f03f1c7 to get more accurate results

@@             Coverage Diff             @@
##            master      #55      +/-   ##
===========================================
- Coverage   100.00%   99.68%   -0.32%     
===========================================
  Files           13       13              
  Lines          321      319       -2     
===========================================
- Hits           321      318       -3     
- Misses           0        1       +1     

Impacted Files	Coverage Δ
src/asgi_lifespan/__version__.py	0.00% <ø> (-100.00%)	⬇️
src/asgi_lifespan/__init__.py	100.00% <100.00%> (ø)

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