Add Codespaces development environment

[cam-schultz]

Context and scope
avalanche-starter-kit links all of the repositories needed to develop on top of Teleporter, a number of example Teleporter applications, and provides local workflows as well as remote workflows via Github codespaces. The envisioned developed experience would be start with avalanche-starter-kit as an introduction to Teleporter development. After working through the simple examples there, developers could "graduate" to teleporter-token-bridge to gain experience with production ready, audited contracts, making modifications to suit their specific needs.

In order to support that workflow, we should seek parity with avalanche-starter-kit for any repo in which smart contracts could be developed by the community. To achieve that, we should port the Dockerfiles and Github Codespaces configuration to this repo.