Add contributing section and link to weekly board to README

[aguschin]

as in MLEM iterative/mlem#389

[codecov-commenter]

Codecov Report

Base: 80.91% // Head: 80.64% // Decreases project coverage by -0.26% ⚠️

Coverage data is based on head (17e11c6) compared to base (691ca4b).
Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #242      +/-   ##
==========================================
- Coverage   80.91%   80.64%   -0.27%     
==========================================
  Files          16       16              
  Lines        1886     1886              
==========================================
- Hits         1526     1521       -5     
- Misses        360      365       +5     

Impacted Files	Coverage Δ
gto/config.py	95.78% <ø> (ø)
gto/cli.py	69.56% <100.00%> (ø)
gto/_version.py	36.36% <0.00%> (-45.46%)	⬇️

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

☔ View full report at Codecov.
📢 Do you have feedback about the report comment? Let us know in this issue.