[docs] Top-level doc showing how to initialize the OpenTelemetry SDK

[CodeBlanch]

Relates to #5325

Changes

• Adds a top-level doc which shows how to initialize the SDK

Merge requirement checklist

• CONTRIBUTING guidelines followed (license requirements, nullable enabled, static analysis, etc.)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.00%. Comparing base (6250307) to head (e639418).
Report is 287 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5762      +/-   ##
==========================================
+ Coverage   83.38%   86.00%   +2.62%     
==========================================
  Files         297      256      -41     
  Lines       12531    11100    -1431     
==========================================
- Hits        10449     9547     -902     
+ Misses       2082     1553     -529     

Flag	Coverage Δ
unittests	?
unittests-Solution	86.00% <ø> (?)

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see 204 files with indirect coverage changes

[github-actions]

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[cijothomas]

Thank you, looks very nice.
(Where to add links to the new readme about initialization- lets discuss it once things are shipped)