docs: Polish up documentation CSS and font

[another-rex]

• Update font to be more readable, Overpass is much harder to read for dense text, and bold text fades into the background. Use more standard text font of Source Sans Pro (3)
• Fix code blocks being very hard to read
• Fix Tables to not have gaps

New version of docs: https://another-rex.github.io/osv-scanner/supported-languages-and-lockfiles/
Old version of docs: https://google.github.io/osv-scanner/supported-languages-and-lockfiles/

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 69.31%. Comparing base (a3a1fc1) to head (2ce6f5a).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1552   +/-   ##
=======================================
  Coverage   69.31%   69.31%           
=======================================
  Files         200      200           
  Lines       19038    19038           
=======================================
  Hits        13196    13196           
  Misses       5135     5135           
  Partials      707      707           

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[cuixq]

the new heading looks not bold enough to me - can we improve this?

[another-rex]

Hmm... I think it looks alright? If you look at just the docs https://just-the-docs.com/docs/ui-components/typography/ it's about the same, I can bump up the font weight a bit, but it's supposed to be thin.

[jess-lowe]

I agree with Xueqin - it feels a little unbalanced. I think having the heading 1 font weight matching the heading 2 font weight feels better (so both at 500). That or bring back Overpass just for the headings - I liked that font lol.

[another-rex]

Reverted the heading fonts to overpass now :) (will take a second to deploy)

[jess-lowe]

Looks great!