Mark files under htmlcov/ as generated

[spenserblack]

Description

This marks files generated by coverage.py, specifically the coverage html command, as generated. There are currently quite a lot of these files that are returned by GitHub's search, and it seems like the large majority come from this tool (more specific search results).

Checklist:

• I am adding new or changing current functionality
  • I have added or updated the tests for the new or changed functionality.

[spenserblack]

I appear to be making some sort of (likely silly) mistake.
Tests fail, but running this locally seems to work fine (got the expected appears to be generated source code output for htmlcov/index.html).

# Doing this in Ruby returns `true`, too
Linguist::Generated.generated?('htmlcov/index.html', lambda { nil })

[spenserblack]

Oh, of course. It helps to actually read the failure message 😅 Moved the check up the chain of ||s so that it's checked before any HTML, JS, or CSS is read.

Anyway, opening it back up for review. I'm anticipating that maybe some method renaming and/or combining with other methods may be requested 🙂

[Alhadis]

Minor nitpick concerning naming; don't forget to move the method definition to its alphabetically-appropriate location in generated.rb Scratch that, the file's not ordered anyway. 😅

[Alhadis]

Nit: it makes more sense to name this htmlcov?, as the method doesn't involve anything more specific than pathname examination.

(If we checked for a substring like <!-- Generated by coverage.py v1.23 --> or what-have-you, then it might make more sense to tie this method to a specific utility).

[spenserblack]

Good point, thanks!