chore: Update Docusaurus deployment workflow and documentation structure

- Added a step to copy screenshots to the static directory during deployment.
- Updated .gitignore to keep the README file in the screenshots directory.
- Added a new README file in the screenshots directory to explain its purpose and usage.
- Introduced a new npm script to prepare screenshots for the documentation site.

docs/static/screenshots/README.md

@@ -0,0 +1,7 @@
+# Screenshots directory
+
+This directory contains copies of the screenshots from the main repository root. These are used in the documentation site.
+
+The contents of this directory are automatically updated by the `prepare-screenshots` script in the package.json file.
+
+Do not manually add files to this directory as they will be overwritten by the scripts.