Remove transpileOnly flag in dev (or make optional)

[leonaves]

https://github.com/oclif/config/blame/a3e3052c4acfece3acd66bab5a13ba7a32f7f6f9/src/ts-node.ts#L42

This means that typechecking doesn't happen during development, which obviously I can see the arguments for, in that it's gonna allow for faster iteration, but personally I'd prefer the command to just fail and force my team to fix their types. I don't know if that's a minority opinion, but if so I would appreciate this at least being somehow optional, perhaps by setting some field in package.json, given that that's read from anyway?