Playground: Better Share, Better Error Handling, General Cleanup

[DogeDark]

This PR:

• Renames ExampleProject struct to Project, introducing the concept of a "Project"
• The Project struct was moved to model out of example-projects
• Projects can be shared via server API which calls to GitHub Gists.
• Server now needs a GIST_AUTH_TOKEN environment variable.
• A new ApiClient struct which acts as a reqwest client for server <-> playground comms.
• AppError was moved to model to help unify a standard error type.
• An Errors struct & context is now provided for components to gracefully push errors which will then be rendered in a modal and logged.
• We now have a monaco_ready signal. It is not yet used everywhere.
• A Cors and br compression layer has been added to the server. Cors is set to permissive.
• Adjusted the template settings for smaller builds (1mb, brotli 400kb instead of 36mb)
• Adds example & target rebuilding so the examples and server is primed at startup!

Closes #418 Closes #419