Add Support for API Key

[alexlmiller]

The CLI uses the Stacks API to build transactions which runs into the 50RPM limit when building big sets of transactions. Need to add the ability to set an API key and authenticate the API calls to get higher limits as it currently 429s once >35 transactions are in a file

trace from error

> start
> npm run cli -- create_tx --csv-inputs txs/ltt-1.csv --out-file txs/ltt-12-txs.json


> cli
> ts-node ./src/index.ts create_tx --csv-inputs txs/ltt-1.csv --out-file txs/ltt-12-txs.json

/Users/alex/Documents/GitHub/multisig-cli/node_modules/@stacks/transactions/src/builders.ts:92
    throw new Error(
          ^
Error: Error fetching nonce. Response 429: Too Many Requests. Attempted to fetch https://stacks-node-api.mainnet.stacks.co/v2/accounts/SM11M6VMKSSW7TCERW2WERT52A5VF95PSK3SS4JMR?proof=0 and failed with the message: "{
  "message":"API rate limit exceeded",
  "request_id":"c8901765bd40e84b2286201205d29c0d"
}"
    at Object.getNonce (/Users/alex/Documents/GitHub/multisig-cli/node_modules/@stacks/transactions/src/builders.ts:92:11)
    at processTicksAndRejections (node:internal/process/task_queues:95:5)