Improve README content rendering and styles

[marcoroth]

For some gems on gem.sh the show page renders very weird and broken looking READMEs, we should look into what's causing it and see if there might be a more relaxed Markdown parser which can also better recover from a malformed markdown file.

It might also be that some of our styles are leaking into the rendered markdown content, maybe we need to better scope the selectors.

Example: https://gem.sh/gems/activerecord/v7.0.6

[ttilberg]

One such issue seems to be related to code blocks with a language specified. I was reviewing a simple gem I wrote and found the readme was looking in disarray.

For example, when the following codeblocks specifying ruby are encountered:

it renders as

and

Link to my example:

• https://gem.sh/gems/output_attributes/v1.0.1
• https://github.com/ttilberg/output_attributes/

I believe the ActiveRecord example is currently suffering the same issue. Fixing the language detection for code blocks might go a long way to resolving the output.

[marcoroth]

@ttilberg improved this a bit in #44, but I think there are still some thing we can improve, like:

• the character escaping mentioned in Correctly render commonly found codeblocks #44
• code highlighting in code blocks
• styles of the stylesheet itself

Also some more advanced features could be cool:

• the ability to copy code from code blocks and the
• Auto-reference constants to the docs page when they are mentioned in the README