Update code snippet for configuring, instantiating and broadcasting transaction using the API Key

[sabbyanandan]

Context from dev (more here):

You should better publish the snippet from Ryan to use api key middleware. That solved my problem

Specifically, https://docs.hiro.so/api-keys#using-the-api-key-in-typescript can be updated with a complete example similar to this test: https://github.com/hirosystems/stacks.js/blob/922e037a6d77141afe0b7d664117ab2955a9507f/packages/transactions/tests/fetchUtil.test.ts#L6-L26

[ryanwaits]

noted: will be updated in docs revamp