docs: Update expired Discord link, and minor documentation fixes

[gin]

Update with Discord link that does not expire.
Created via Discord channel menu -> Invite People -> Edit invite link -> Expire After: "Never" -> Generate a New Link

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.

[thehowl]

LGTM

[thehowl]

Thanks!

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 55.57%. Comparing base (0e3c050) to head (33af27b).
Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2634      +/-   ##
==========================================
+ Coverage   54.99%   55.57%   +0.57%     
==========================================
  Files         595      581      -14     
  Lines       79775    78939     -836     
==========================================
- Hits        43872    43867       -5     
+ Misses      32581    31749     -832     
- Partials     3322     3323       +1     

Flag	Coverage Δ
contribs/gnodev	60.58% <ø> (+34.58%)	⬆️
misc/genstd	80.54% <ø> (ø)

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