ci: add docs check job

[oleonardolima]

Description

As we are adding in bitcoindevkit/bdk#2158, this PR adds a new CI job and justfile recipe to check for the documentation.

Notes to the reviewers

I'm still unsure how to fix the warning on changeset.rs, any suggestions are welcome.

Changelog notice

### Added

- ci: add new `docs_check` job to check for any error or warning in docs.

### Changed

- fix(docs): use correct `intra_doc_links`.

Checklists

All Submissions:

• I've signed all my commits
• I followed the contribution guidelines
• I ran just p before pushing

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.04%. Comparing base (4d4adae) to head (4d2e398).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #416      +/-   ##
==========================================
+ Coverage   79.93%   80.04%   +0.10%     
==========================================
  Files          24       24              
  Lines        5287     5336      +49     
  Branches      241      242       +1     
==========================================
+ Hits         4226     4271      +45     
- Misses        984      987       +3     
- Partials       77       78       +1     

Flag	Coverage Δ
rust	80.04% <ø> (+0.10%)	⬆️

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[luisschwab]

ACK 4d2e398