Set up source code formatters (prettier, etc.) #394
Description
I've noticed many style changes in this PR but looks like we don't have prettier configured in this repository. I suggest we use the one from StarkNet integration and we reformat the codebase one more time: https://github.com/smartcontractkit/chainlink-starknet/blob/develop/.prettierrc.json
Originally posted by @krebernisak in #380 (comment)