[CD-553] moving docs to this repo

[rupl]

CD-553

Types of changes

• ✔️ Improvement (non-breaking change which iterates on an existing feature)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Security update (dependency updates, or to fix a vulnerability)

Description

Updates to docs based on content within our old Google Drive (now SharePoint) but in general trying to move developer notes about the theme into the README / instructions here.

Steps to reproduce the problem or Steps to test

Docs only. No testing needed.

Impact

Docs only. No impact.

PR Checklist

• I have followed the Conventional Commits guidelines.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have made changes to the sub theme to reflect those in the base theme

[lazysoundsystem]

All clear. Thanks!