docs: Note about `main` branch and black lives matters

[tgrrr]

What: add note about production being from main branch Why: to support black lives matters

What type of PR is this? (check all applicable)

• [x] 📝 Documentation

Context

https://www.zdnet.com/article/github-to-replace-master-with-alternative-term-to-avoid-slavery-references/

Did you add documentation?

• [x] 📜 readme.md

[codecov[bot]]

Codecov Report

:exclamation: No coverage uploaded for pull request base (main@2611abd). Click here to learn what that means. The diff coverage is n/a.

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  Hits            ?      434           
  Misses          ?       84           
  Partials        ?        0           

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