Check that public members and functions DONT start with an underscore

[97gamjak]

Fixes #140

[codecov]

Codecov Report

❌ Patch coverage is 92.20779% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 87.04%. Comparing base (4aa13f7) to head (a10b015).
⚠️ Report is 1 commits behind head on dev.

Files with missing lines	Patch %	Lines
...ast/checks/enforce_no_public_leading_underscore.py	92.10%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##              dev     #142      +/-   ##
==========================================
+ Coverage   86.83%   87.04%   +0.21%     
==========================================
  Files          53       54       +1     
  Lines        1838     1915      +77     
==========================================
+ Hits         1596     1667      +71     
- Misses        242      248       +6     

Flag	Coverage Δ
unittests	87.04% <92.20%> (+0.21%)	⬆️

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