Write more redirect stubs

[lilyminium]

Fixes #

Changes made in this Pull Request:

• Redirect URLs like https://docs.mdanalysis.org/documentation_pages/converters.html to https://docs.mdanalysis.org/1.0.0/documentation_pages/converters.html

This allows us to get rid of the PageRule currently doing this so we can redirect www.mdanalysis.org/docs -> docs.mdanalysis.org :-)

PR Checklist

• Tests?
• Docs?
• CHANGELOG updated?
• Issue raised/referenced?

[codecov]

Codecov Report

Merging #2955 into develop will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff            @@
##           develop    #2955   +/-   ##
========================================
  Coverage    93.05%   93.05%           
========================================
  Files          186      186           
  Lines        24609    24609           
  Branches      3187     3187           
========================================
  Hits         22900    22900           
  Misses        1661     1661           
  Partials        48       48           

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[orbeckst]

LGTM.

Same as PR #2960 (for master).