Update default branch to main

[davidcheung]

1. zero-backend-node/scripts/gha-setup.sh

   Lines 37 to 38 in fdd5138

   	DEFAULT_BRANCH=master
   	curl -XPUT "https://api.github.com/repos/$GITHUB_ORG/$GITHUB_REPO/branches/$DEFAULT_BRANCH/protection" \

probably can do the same as commitdev/zero#424 and run git config --get init.defaultBranch with a default

2. In circleci pipeline

   zero-backend-node/templates/.circleci/config.yml

   Lines 312 to 313 in 1376ac0

   	only: # only branches matching the below regex filters will run
   	- /^master$/

   
   we could just update so it supports both in a regex /^(master|main)$/ or something like that