Add Aliki-based styles to RubygemsHelper#simple_markup output

[Kerrick]

Hello,

I noticed recently that RubygemsHelper has a simple_markup method that detects the presence of an RDoc h2+ in a gem specification's description. It only activates when there is an h2+ present in the gem__desc, so it only applies to gems that get simple_markup applied. (Edited: See next comment.)

rubygems.org/app/helpers/rubygems_helper.rb

Lines 26 to 34 in 5b588b9

	def simple_markup(text)
	if /^==+ [A-Z]/.match?(text)
	options = RDoc::Options.new
	options.pipe = true
	sanitize RDoc::Markup.new.convert(text, RDoc::Markup::ToHtml.new(options))
	else
	tag.p(escape_once(sanitize(text.strip)))
	end
	end

This pull request adds styles based on @st0012's Aliki, the new default RDoc theme, combined with RubyGems.org's existing styles. It has the the same relative font sizes and weights, and the same relative margins and padding, as Aliki. It uses the same colors as RubyGems.org.

I know #5802 is coming eventually, but this can really elevate the gem info page in the mean time. Please see below for before & after screenshots.

Note

This hides image tags, because the current content security policy blocks them from being displayed.

Before

After

---

This pull request was created without any contribution from a generative AI. declare-ai.org

[Kerrick]

I added an optional second commit that flips the heuristic. Rather than only activating when there is an h2+ present in the gem__desc, it activates when there is anything but a single p present. That way if the RubygemsHelper#simple_markup heuristic ever changes, this will be more resilient.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.48%. Comparing base (5b588b9) to head (5d81518).
⚠️ Report is 6 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6228      +/-   ##
==========================================
- Coverage   97.26%   94.48%   -2.79%     
==========================================
  Files         477      480       +3     
  Lines        9871    10059     +188     
==========================================
- Hits         9601     9504      -97     
- Misses        270      555     +285     

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