Rename master to main

[joeyAghion]

As per docs.

Positron docs have lots of deep links into other repos' (Force, Reaction, Potential, Fulcrum) source. Since those haven't been updated yet and I didn't want to break the links, I left master within those URLs. If they are renamed in the future, Github will redirect these URLs to the updated location.

To update local checkouts, developers should do:

git checkout master
git branch -m master main
git fetch origin
git branch -u origin/main main
git remote set-head origin -a

[codecov[bot]]

Codecov Report

Merging #3020 (d1c760c) into main (e1a5a3f) will decrease coverage by 13.8%. The diff coverage is n/a.

@@           Coverage Diff            @@
##            main   #3020      +/-   ##
========================================
- Coverage   83.1%   69.2%   -13.9%     
========================================
  Files        196     288      +92     
  Lines       5380    8104    +2724     
  Branches     988    1151     +163     
========================================
+ Hits        4474    5613    +1139     
- Misses       654    2226    +1572     
- Partials     252     265      +13