Documentation website tweaks

[AlekSi]

• Make "Edit this page" links work.
• Remove /docs/ from URLs.

Readiness checklist

• I added tests for new functionality or bugfixes.
• I ran task all, and it passed.
• I added/updated comments for both exported and unexported top-level declarations (functions, types, etc).
• I checked comments rendering with task godocs.
• I ensured that the title is good enough for the changelog.
• (for maintainers only) I set Reviewers (@FerretDB/core), Assignee, Labels, Project and project's Sprint fields.
• I marked all done items in this checklist.

[vercel]

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Name	Status	Preview	Updated
ferret-db	✅ Ready (Inspect)	Visit Preview	Sep 27, 2022 at 8:21AM (UTC)

[codecov]

Codecov Report

Merging #1183 (5df00bb) into main (9c1e684) will decrease coverage by 0.09%.
The diff coverage is n/a.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1183      +/-   ##
==========================================
- Coverage   66.26%   66.16%   -0.10%     
==========================================
  Files         250      250              
  Lines       12260    12260              
==========================================
- Hits         8124     8112      -12     
- Misses       3246     3254       +8     
- Partials      890      894       +4     

Impacted Files	Coverage Δ
internal/util/version/version.go	55.00% <0.00%> (-5.00%)	⬇️
internal/handlers/common/filter.go	86.01% <0.00%> (-0.94%)	⬇️

Flag	Coverage Δ
integration	62.45% <ø> (-0.10%)	⬇️
mongodb	14.80% <ø> (-0.03%)	⬇️
pg	51.86% <ø> (-0.10%)	⬇️
tigris	34.44% <ø> (-0.03%)	⬇️
unit	23.99% <ø> (-0.03%)	⬇️

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