docs: add experimental mark for examples

[qweeah]

What this PR does / why we need it:

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #1568

Please check the following list:

• Does the affected code have corresponding tests, e.g. unit test, E2E test?
• Does this change require a documentation update?
• Does this introduce breaking changes that would require an announcement or bumping the major version?
• Do all new files have an appropriate license header?

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.07%. Comparing base (363dc2d) to head (a52e974).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1569   +/-   ##
=======================================
  Coverage   84.07%   84.07%           
=======================================
  Files         119      119           
  Lines        5325     5325           
=======================================
  Hits         4477     4477           
  Misses        602      602           
  Partials      246      246           

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[shizhMSFT]

LGTM