Proofread for v5.5 release

[MaximMoinat]

Main changes:

• Updated the readme and index page to reflect that v5.5 is the latest release
• Updated tooling support for v5.5
• Adds two pages to the menu, that were only referenced in text before "How to Calculate Drug Dose" and "Observation Period Considerations for EHR Data"
• Small fixes to the v5.5 specification

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 57.89%. Comparing base (fd40a04) to head (e0aab0a).
⚠️ Report is 11 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #806      +/-   ##
===========================================
+ Coverage    57.25%   57.89%   +0.64%     
===========================================
  Files            8        8              
  Lines          262      266       +4     
===========================================
+ Hits           150      154       +4     
  Misses         112      112              

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