Allow only linting comments matching a pattern, e.g. //! and /// in rust instead of //

[ModProg]

Is your feature request related to a problem? Please describe.
I like to use ltex to spellcheck my documentation comments (they are markdown so something that generally plays nicely with ltex, especially after #238).
Normal comments // are much less important and often times are also used to comment out code, therefor I'd like to exclude them from linting.

Describe the solution you'd like
Have a setting to either, specify a custom regex for what to lint, or support a dedicated setting, i.e., check-doc-comments-only.