Make `dev-deploy.sh` only deploy contract when it changes

RN, `dev-deploy.sh` always redeploys the contract. This is slow, unnecessary, and it bloats NEAR's testnet.

Tasks:
- [ ] Create a script that: 1) checksums the contract source, 2) if a checksum file (let's call it `contract.sum`) DNE or it contains a different checksum, then write to the checksum file and output a truthy value, otherwise output a falsy value
- [ ] In `dev-deploy.sh`, only deploy the contract if the checksum script outputs a truthy value.

Start by reading dev-deploy.sh and locating the contract source it deploys. Review how the deployment command is invoked, then verify the checksum script's truthy and falsy outcomes and confirm that repeated runs skip unchanged contracts while changed contracts still deploy.

Written by the indexing model from the issue text.