Expose highlighting info to SQL

[nishanthkarthik]

Is your feature request related to a problem? Please describe.
I use highlights a lot. I would like to filter-in lines that have at least one highlighted match.

Describe the solution you'd like
Expose highlights info over SQL so I can write my own command.

Describe alternatives you've considered
This could be a first-party command like :filter-highlighted but I am not sure if my use case is common.

[tstack]

This sounds reasonable. The expressions that are added via :highlight could be exposed through a SQLite vtable. Then, you should be able to do what you want.

that have at least one highlighted match

Note that highlights are currently a display-only thing. lnav doesn't scan the files looking for matches.