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

[Sladuca]

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.