CMCL-0000: Documentation bug bash

[sebastienduverne]

Purpose of this PR

Various documentation fixes according to user feedback tickets. We do this in a context of doc team bug bash.

• DOCATT-5679 - Spline example screenshot update to version 3 + link to Splines documentation
• DOCATT-5052 - Cinemachine Blender Settings asset reference page update + navigation to related topics
• DOCATT-5841 - Cinemachine Third Person Aim extension reference page cleanup + bonus content provided by Greg

Testing:

• Doc build was successful and log is clean (fixed broken link)

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 26.98%. Comparing base (29a5e80) to head (2813bfe).

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Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1007   +/-   ##
=======================================
  Coverage   26.98%   26.98%           
=======================================
  Files         253      253           
  Lines       28405    28405           
=======================================
  Hits         7664     7664           
  Misses      20741    20741           

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