Auto update bot

Automatically update the PKGBUILD on AUR when there is a new version of a package.

Warning

We have implemented the test mechanism but the documents haven't been updated yet.

Add AutoUpdateBot as a co-maintainer of your package on AUR.
Add the corresponding nvchecker configuration under config. You can locally test your newly added configuration with:
```
python nvchecker.py config/path/to/the_added_package.yaml
nvchecker -c nvchecker.toml -e the_added_package
```
(Optional) Write a custom update script to config/path/to/the_added_package.override to override bin/update-pkgver if necessary.
Create a pull request to submit your changes and pass the checks.
- Remember to take a look at the check results.
Done. You can check the outputs of GitHub Actions if there is anything wrong.
- It runs every day.