Renamed default branch to main

Anyone who has the repository already cloned will likely need to update it. These are the commands Github suggests:

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

The issue names no repository file, test, or entry point; it only provides GitHub's commands for renaming a local branch and updating its remote tracking. Start by checking whether any repository documentation or configuration still refers to the old default branch, and consider the work done only when the affected references and guidance are identified.

Scritto dal modello di indicizzazione a partire dal testo della issue.