Add typing hints

[SchoolGuy]

This PR does two things:

• Add typing hints and docstrings to some of the functionality of this repository
• Fix typos in the documentation

[coolo]

Please either avoid the complex types or make them proper class

[codecov-commenter]

Codecov Report

Base: 28.49% // Head: 28.50% // Increases project coverage by +0.01% 🎉

Coverage data is based on head (3a20df6) compared to base (aad2291).
Patch coverage: 49.36% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2877      +/-   ##
==========================================
+ Coverage   28.49%   28.50%   +0.01%     
==========================================
  Files          84       84              
  Lines       14442    14467      +25     
==========================================
+ Hits         4115     4124       +9     
- Misses      10327    10343      +16     

Impacted Files	Coverage Δ
pkglistgen/cli.py	0.00% <0.00%> (ø)
pkglistgen/tool.py	0.00% <0.00%> (ø)
osclib/pkglistgen_comments.py	18.50% <47.69%> (+1.62%)	⬆️
osclib/core.py	58.41% <100.00%> (+0.05%)	⬆️
osclib/stagingapi.py	59.04% <100.00%> (-0.34%)	⬇️
osclib/accept_command.py	73.51% <0.00%> (+0.33%)	⬆️

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