Update local links to links that work on charmhub

[jdkandersson]

As a documentation writer I want to include links to other parts of the documentation so that users can go to that section.

The local relative links should be updated to the correct links so that they work on charmhub. E.g., a link from tutorials/getting-started should be updated to a link to the topic before the documentation is published

[jdkandersson]

This should be done in the discourse interface and needs to be translated back when a topic is retrieved. It can possible come with some logical arguments to indicate the need to replace something and also communicate back in that way since discourse should not necessarily need to understand how links work in the source repository