[Feature Request] Start server in scratchpad

[lorensr]

Is your feature request related to a problem? Please describe.

If I try to run ts-node scratchpad/scratchpad.ts, after a while I get this error:

ts-node scratchpad.ts
TransportError: tonic::transport::Error(Transport, hyper::Error(Connect, ConnectError("tcp connect error", Os { code: 61, kind: ConnectionRefused, message: "Connection refused" })))
    at Function.connect (/Users/me/node_modules/@temporalio/worker/src/connection.ts:51:15)
    at async Function.create (/Users/me/node_modules/@temporalio/worker/src/worker.ts:457:47)
    at async main (/Users/me/gh/samples-typescript/scratchpad/scratchpad.ts:33:18)

Describe the solution you'd like

scratchpad.ts runs temporal server start-dev if it's not already running

cc @dandavison