feat(gnoweb): source code viewer improvements

[0xtekgrinder]

Improve the source code viewer with several changes:

• Fix & instead of &;
• Add a link to imported modules
• Add a a line counter

closes #2746

Contributors' checklist...

• Added new tests, or not needed, or not feasible
• Provided an example (e.g. screenshot) to aid review or the PR is self-explanatory
• Updated the official documentation or not needed
• No breaking changes were made, or a BREAKING CHANGE: xxx message was included in the description
• Added references to related issues and PRs
• Provided any useful hints for running manual tests
• Added new benchmarks to generated graphs, if any. More info here.

[0xtekgrinder]

So far, I have added a line counter but I don't really see how we can achieve a permalink as we sanitize the html removing all onclick attributes so we cannot really do simple highlighting logic + copying permalink

@moul @zivkovicmilos

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 60.86%. Comparing base (01ee5a9) to head (37abf1c).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2757      +/-   ##
==========================================
+ Coverage   60.84%   60.86%   +0.01%     
==========================================
  Files         563      563              
  Lines       75190    75190              
==========================================
+ Hits        45753    45766      +13     
+ Misses      26068    26057      -11     
+ Partials     3369     3367       -2     

Flag	Coverage Δ
contribs/gnodev	60.65% <ø> (ø)
contribs/gnofaucet	14.46% <ø> (ø)
gno.land	67.17% <ø> (ø)
misc/logos	20.23% <ø> (+0.35%)	⬆️
tm2	62.10% <ø> (+0.10%)	⬆️

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[leohhhn]

Hey, checked out gnoweb with this PR. Seems that the import links only work for the first link in the series. Take a look and see if you can fix this. Also, it would be great if the imports weren't constantly underlined, but only upon mouse hover.
Also, when you underline them, I think excluding the quotation marks looks a bit better :)

[0xtekgrinder]

Hello @leohhhn I have fixed the import of link only for the first + implemented the style overhaul you suggested

[thehowl]

Thank you for the contribution. Some work needed; let's focus on the esthetical changes for now and we can tackle the imports at a later time.

[jefft0]

Removed the "review team" label because this is already reviewed by core devs.