[TS types] can we have camel casing for field names?

Currently it's snake_cased: https://github.com/apex/rpc/blob/master/generators/tstypes/testdata/todo_types.ts#L4

I'm using [prettier](https://github.com/prettier/prettier) on my codebase which is a very opinionated code formatter and I guess many other people are too considering the number of stars it has on github.

Prettier is strict about using camelCasing for object field names so it gives me very annoying eslint errors when I try to instantiate api types.

It would be great if we had a flag in the generator to generate camelCased fields instead. WDYT?