Initial proof of concept

[sisyphusSmiling]

Issue To Be Solved

We'll want an initial working prototype the build the basis on which to build and iterate on in keeping with the design proposed in onflow/flips#233

Suggest A Solution

The most approachable bridging use case is a Flow-native NFT bridging from Flow to EVM and back. This should include a primary bridge contract which configures itself to lock the NFT on the Cadence side and a bridge-controlled ERC721 to mint upon bridging to EVM. On briding back from EVM, the bridge should burn the ERC721 NFT and unlock the previously locked NFT.