Syntax highlighting in doctest comments?

I've been using the Eval Plugin of HLS, which provides us with a pleasant alternative for REPL.
That plugin provides a way to evaluate (or execute some simple ghci-like commands such as `type`) codes in doctest style comment: `-- >>>`.
The result is appended as line comments right after the doctest comments.

In some situation, both of the inputs and outputs of doctest comments can be relatively long.
I think it might be useful if VSCode also highlights the contents inside the doctest comments and comments that immediately follow.

In short: currently, we have the following:


And it might be good if this becomes (with a less bright colour than in the standard code block):


If I understand correctly, there is a VSCode API to change text-decorations dynamically.
Or, perhaps this should be resolved upstream, i.e. might be reported to [JustusAdam/language-haskell](https://github.com/JustusAdam/language-haskell)?