style: Added black formatting & refactored configs into pyproject.toml

[frgfm]

This PR introduces the following modifications:

• fixes the collect_env script
• moves all configs into pyproject.toml (cf. PEP 518), apart from flake8 that doesn't support it (cf. pyproject.toml (PEP 518) support PyCQA/flake8#234)
• adds black as code formatter
• applies black on the codebase
• made mypy stricter and fixed typing

[codecov]

Codecov Report

Merging #58 (90f82de) into master (0032f78) will decrease coverage by 0.26%.
The diff coverage is 71.20%.

@@            Coverage Diff             @@
##           master      #58      +/-   ##
==========================================
- Coverage   88.37%   88.10%   -0.27%     
==========================================
  Files          10       10              
  Lines         671      656      -15     
==========================================
- Hits          593      578      -15     
  Misses         78       78              

Impacted Files	Coverage Δ
torchscan/modules/receptive.py	64.86% <42.85%> (ø)
torchscan/utils.py	75.00% <53.57%> (ø)
torchscan/crawler.py	82.08% <84.61%> (ø)
torchscan/modules/flops.py	97.48% <100.00%> (-0.10%)	⬇️
torchscan/modules/macs.py	100.00% <100.00%> (ø)
torchscan/modules/memory.py	100.00% <100.00%> (ø)
torchscan/process/memory.py	71.42% <100.00%> (ø)