CCM-22947: dropping docs

[aidenvaines-cgi]

Description

• Removes the obsolete Jekyll documentation site
• Removed the artefact-jekyll-docs job from the stage 3 build workflow.
• Removed the documentation accessibility test from the stage 4 acceptance workflow.
• Removed the GitHub Pages deployment and documentation refresh workflows.
• Deleted the local Jekyll build action and the docs/ directory.
• Removed stale documentation references from repository configuration, templates, and development settings.
• Added a root-level CONTRIBUTING.md and updated the PR template to reference it.
• Updated the README to direct contributors to Confluence for NHS Notify Internal documentation.

Context

Type of changes

• Refactoring (non-breaking change)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would change existing functionality)
• Bug fix (non-breaking change which fixes an issue)

Checklist

• I am familiar with the contributing guidelines
• I have followed the code style of the project
• I have added tests to cover my changes
• I have updated the documentation accordingly
• This PR is a result of pair or mob programming

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Sensitive Information Declaration

To ensure the utmost confidentiality and protect your and others privacy, we kindly ask you to NOT including PII (Personal Identifiable Information) / PID (Personal Identifiable Data) or any other sensitive data in this PR (Pull Request) and the codebase changes. We will remove any PR that do contain any sensitive information. We really appreciate your cooperation in this matter.

• I confirm that neither PII/PID nor sensitive data are included in this PR and the codebase changes.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud