Add simple service example

[hayleyjames]

This change adds an example based on go-kit's stringsvc1 example. I don't know how your services are organized, so I used a generic project format. The business logic is separated from the transport layer, and there is a client for calling the service.

I hope this might be useful for someone.

Thanks,
Josh

[obeattie]

Sorry for taking so long to respond to this and thanks for the PR!

While I'd love to include more examples in the repo, this does not seem very minimal. I would prefer if any examples focussed on direct use of the library rather than trying to promote conventions for the structure of calling code. What you have here is very different to how we use Typhon within Monzo, for example.

Does this make sense?

[obeattie]

Please feel free re-open if you are interested in refining the example 😄