Move Rebuff Playground Server to it's own repository

[seanpmorgan]

Currently, Rebuff exists as a monolith repo with a TS Rebuff SDK, Prompt hacking game, Playground server, and python SDK to interact with the playground server.

While the playground is a great example of how to use the rebuff SDK, it makes more sense as a stand alone repository that uses a published version of the Rebuff npm package: #53

We will continue to run the playground server and build on its user friendliness (e.g. how to obtain more credits).

[seanpmorgan]

This move would include moving the current python SDK which is a means of interacting with the playground server.