docs: remove demo-app docs

[ajcasagrande]

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PR Checklist

Please check if your PR fulfills the following requirements:

• [X] I am not introducing a breaking change (if you are, flag in conventional commit message with BREAKING CHANGE: describing the break)
• [X] I am not introducing a new dependency (add notes below if you are)
• [N/A] I have added unit tests for the new feature or bug fix (if not, why?)
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[codecov-commenter]

Codecov Report

Merging #273 (ee4e5af) into main (35e0b63) will not change coverage. The diff coverage is n/a.

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@@           Coverage Diff           @@
##             main     #273   +/-   ##
=======================================
  Coverage   33.53%   33.53%           
=======================================
  Files          18       18           
  Lines        1792     1792           
=======================================
  Hits          601      601           
  Misses       1125     1125           
  Partials       66       66           

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