Support optional rendering of `AnnotationType` type prefix like "note:", "help:", "hint:", etc.

[ironcev]

Perhaps this functionality already exists, but I couldn't find it in any of the options, I also didn't see how it could be manipulated in the resulting DisplayList.

By default, the prefix that denotes the AnnotationType is not rendered for errors and warnings, but it is for all other types of annotations. In the output of the Sway compiler we need the flexibility to show the prefix for some annotations, and for some not.

Consider the following output of the Sway compiler:

We want to have the help: prefix in the footer, but not the info: prefix in the code snippet. In general, we do not want to have any prefixes in the code snippet.

Is there a way already to achieve this functionality?

If not, I would be glad to contribute and implement it.

[epage]

#97 would add a way to annotate "context" which is independent of Level.

[epage]

I believe this was fixed by #195, so I'm closing this. If there is something I missed, let us know!