CMCL-0000: Add user manual page for SimplePlayerController sample code

[glabute]

Purpose of this PR

The Cinemachine Samples have received some attention from the field. People like them, and they like the Simple Character Controller code that ships with them.

There is a feeling that CM's controller is easier to use and to customize than Unity's Standard Assets. We want to promote the usage of CM sample code, and for this reason it is interesting to add some user-facing documentation.

This PR is a first pass at that.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 27.16%. Comparing base (99eed58) to head (8f237ad).
Report is 6 commits behind head on main.

❗ Current head 8f237ad differs from pull request most recent head cf7259a

Please upload reports for the commit cf7259a to get more accurate results.

❗ Your organization needs to install the Codecov GitHub app to enable full functionality.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1004   +/-   ##
=======================================
  Coverage   27.16%   27.16%           
=======================================
  Files         250      250           
  Lines       27958    27958           
=======================================
  Hits         7596     7596           
  Misses      20362    20362           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[sebastienduverne]

• A few corrections and suggestions in manual, API docs, and tooltips.
• Requirement: please add an entry to the new file in the TableOfContents.md – I'd say as the last child of the samples-tutorials.md page.

[glabute]

All issues resolved