Changing custom properties

[R4vio]

The current library has only the possibility to GET custom properties, while the API has to option to also PATCH as can be seen here:
https://docs.github.com/en/rest/repos/custom-properties?apiVersion=2022-11-28#create-or-update-custom-property-values-for-a-repository

It would be nice if this feature would be included in the library

[gmlewis]

This would be a great PR for any new contributor to this repo or a new Go developer.
All contributions are greatly appreciated!

Feel free to volunteer for any issue and the issue can be assigned to you so that others don't attempt to duplicate the work.

Please check out our CONTRIBUTING.md guide to get started. (In particular, please remember to go generate ./... and don't use force-push to your PRs.)

Thank you!

[HariCharan-001]

I'd like to work on this.

[gmlewis]

I'd like to work on this.

Thank you, @HariCharan-001 ! It's yours.

[HariCharan-001]

Submitted a PR, please review !

[HariCharan-001]

Raised a new PR !