Waltham documentation

Write documentation about waltham to make anyone can understand/use it if they want.
HowTo is confirmed during a call (22nd July)

>There was a question today during the UI and Graphics EG call about how to add to the documentation. Scott Rifenbark has been working on improving the AGL documentation site. >This link [1] documents how to add to the AGL documentation.
>[1] https://docs.automotivelinux.org/docs/en/master/howto/reference/handle-docs/handle-docs.html