Create new screencast automatically on docs build

[pjbull]

Uses mkdocs-termynal to automatically create a new screencast recording when the docs build.

• Add mkdocs-gen-files to run scripts as part of the mkdocs build
• Add a script docs/scripts/generate-termynal.py to generate docs/_partials/termynal.md with the output from running CCDS.
• Use mkdocs-include-markdown-plugin to incorporate the generated docs/_partials/termynal.md in index.md
• Add the mkdocs-termynal plugin to add replay for the terminal session in the docs.
• Add some CSS/JS tweaks to make things look nice and smooth.