Move from master to main

[hemish11]

Recently, Github has changed the master branch to main, so we should also take this step and change the branch of a flutter from master to main.

Here are all the commands that need to run to make a clone of this branch with a different name:
git branch -m master main
git push -u origin main
git symbolic-ref refs/remotes/origin/HEAD refs/remotes/origin/main

After all this, we need to change the default branch from the settings of the repo.

And finally, run this command to delete the master branch
git push origin --delete master

Thanks a lot.