Please add documentation

[Darren-Vine]

We had big problems using this because of lack of documentation anywhere:

Please add where to create a ticket to get an app created for the users repos (DOST)
What to request in the ticket
Where to modify the settings of the app (https://github.com/organizations/philips-internal/settings/apps)
How to generate the token (add secret -> base64 private-key.pem > base64->pem
What security settings to set
How this gets approved (email) -> link to update
What variables to add/set in the repo.

This took us 5 working days and a lot of effort to with multiple people.

It would actually be better if there was a default app for the entire organisation with organisation level tokens that could be used.