Split blocks out of single development build

Currently the blocks in this repo are, during development, treated as a single plugin. They are then packaged up and released as individual plugins.

This creates a difference between development and production environments, particularly when it comes to the inclusion of resources.

It would be better if we treated this more as a mono repo with multiple plugins, with each plugin being a separate block. This would additionally allow blocks to contain build steps specific to them (for example, the layout grid).

Ideally this could be done in a way that maintains a common set of build tools and block structure.