Add support for static files

[audreyfeldroy]

Add functionality to copy static files from the input directory to the public directory.

• StaticSiteGenerator class:

  • Add copy_static_files method to copy static files from input to public.
  • Call copy_static_files method in the build method after rendering templates.

• Main function:

  • Call the copy_static_files method after building the site in the main function.

• README.md:

  • Add instructions for adding static files to the input directory.
  • Explain that static files will be copied to the public directory.

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For more details, open the Copilot Workspace session.

[audreyfeldroy]

Thank you for this. Kindly add a test that copies a tiny static file and checks that the resulting copy is present.