ci: fix docker caching by switching to buildx driver

[AlexCannonball]

Overview

Fixes #123
This PR fixes the Docker caching issues.

Proposed Changes

• Added docker/setup-buildx-action to enable the docker-container driver (required for registry caching).
• Restored cacheTo in the Pre-build workflow.

🛠 Action Required from the owner

To resolve the 403 Forbidden errors and enable the cache, please:

1. Go to the Package Settings for protols/devcontainer.
2. Change Package Visibility to Public.
3. Under Manage Actions access, ensure the repository is added with at least Read access.

Once these steps are completed, the cacheFrom and cacheTo instructions will hopefully become fully operational.