Add example notebook and readme to files folder inside dist

[mcbarton]

Description

Please include a summary of changes, motivation and context for this PR.

@vgvassilev @anutosh491 Currently the example notebook and readme.md is not showing up in the Jupyter Lite demo. Based on the fact that the files for the jupyter lite xeus-python demo are in a folder called files (see https://jupyterlite.github.io/xeus-python-demo/files/README.md) I have modified the ci to make this folder in the build folder dist (if not present already), and them move the files we need into the folder accordingly to try and fix the problem we are having.

Fixes # (issue)

Type of change

Please tick all options which are relevant.

• Bug fix
• New feature
• Added/removed dependencies
• Required documentation updates

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.05%. Comparing base (0aad6f8) to head (bedb3c6).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #147   +/-   ##
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  Coverage   82.05%   82.05%           
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  Files          17       17           
  Lines         613      613           
  Branches       59       59           
=======================================
  Hits          503      503           
  Misses        110      110