Pull developer documentation on tokens out of CiviMail
The token reference is currently found here: https://docs.civicrm.org/dev/en/latest/framework/civimail/#tokens
This might have made sense a while ago, but tokens are now more that just a CiviMail thing. They are like a mail merge functionality (not quite a templating language, I guess, but almost) that has applications (current and potential) in other parts of the system. e.g. I am using them in chatbot.
It would be good to create https://docs.civicrm.org/dev/en/latest/framework/tokens and have them live there.