4903: Add highlighting support for doc comments r=matklad a=Nashenas88
The language server protocol includes a semantic modifier for documentation. This change exports that modifier for doc comments so users can choose to highlight them differently compared to regular comments.
Example:
<img width="375" alt="Screen Shot 2020-06-16 at 10 34 14 AM" src="https://user-images.githubusercontent.com/1673130/84788271-f6599580-afbc-11ea-96e5-7a0215da620b.png">
CC @woody77
Co-authored-by: Paul Daniel Faria <Nashenas88@users.noreply.github.com>
This commit adds a function that tries to determine the syntax highlighting class of NAME_REFs based on the usage.
It is used for highlighting injections (such as highlighting of doctests) as the semantic logic will most of the time result in unresolved references.
It also adds a color to unresolved references in HTML encoding.
