docs: Adjust samples list to make it available for the main Uno doc and keeping it in sync with the main ReadMe & add ci build stages

[agneszitte]

Related issue: https://github.com/unoplatform/uno/issues/16140

Summary of Changes

Preparation for External Samples List Documentation Update:

Initiating steps to update the external samples list documentation for the Uno repository. This involves the introduction of a main doc folder and a related toc.yml.

[!NOTE] Next Steps: Once the necessary changes are finalized, we'll be able to integrate them by taking the commit ID and updating it in the doc/import_external_docs.ps1 of the Uno repository, as follows: @("https://github.com/unoplatform/uno.samples", "uno.samples", "INSERT_COMMIT_HASH_OR_BRANCH_NAME")

Automated Synchronization of Samples List:

To keep the samples list in sync between the Uno Platform's general documentation and the main README for Uno.Samples, this PR introduces changes to automate the inclusion of doc/includes/samples-list.md in the CI build process.

[!WARNING] Reason: GitHub Markdown does not support direct includes at the moment, which limits our ability to display the list directly on the GitHub Uno.Samples main repository page.

[!IMPORTANT] Samples list in README.md should not be updated manually. Changes will be only made in doc/includes/samples-list.md. The automated process will ensure these changes are reflected in the main README.md The tags surrounding the samples list in README.md are crucial for this automation to work correctly (see build/update-readme-samples-list.yml for the related script).

CI Build Process Enhancements:

This PR introduced new stages in the CI pipeline to enhance the build process. These stages are designed to wait for a proper determination of changes, ensuring that the pipeline builds under the right conditions.

Conditional Sample Builds:

The pipeline has been adjusted to prevent the building of samples when only documentation changes are detected. This optimization ensures resources are used efficiently, focusing build efforts where they are needed based on the nature of the changes made.