Tonic Relection needs a readme/howto

## Feature Request

### Crates

tonic_reflection

### Motivation

There are no usage examples and I had to reverse engineer the crate to use it.

### Proposal

There should be a readme and/or crate documentation illustrating how to use tonic_reflection

### Alternatives

Scour the web/roll my own, which made it hard to use the crate.