Refactor: Preparing for WC Integration

[bh2smith]

While working on #34, I noticed some redundancies, inconsistencies and non-necessities in the existing code. Realistically we should rework the design of this package (while its still pre-v1).

• lint configuration was cleaned up by prettier (also adding indentation to switch cases).
• ignore lint config file going forward.
• populate transaction method removing complexity from adapter (Will also be used by WC Router).
• pickValidSignature did not need to be part of the adapter class.
• MPCContract.encodeSignatureRequestTx didn't need to be async.
• Adding optional gas limit to BaseTx (since it is provided by WC session request payload). When included we can skip an rpc call.
• documentation type (De)serializedTx
• Introducing a method toPayload that builds number array of bytes for MPC contract.