Nighthawk releases

Nighthawk releases: Users should not have to build the binary

*Description*:
Users should not have to build the binary e.g. some folks might not have the right environment, familiarity with the toolchain, etc. IMO, this is a lot of friction when using Nighthawk. Instead we should either provide occasional release binaries and / or instructions to extract the binaries from the [dockerhub](https://hub.docker.com/r/envoyproxy/nighthawk-dev/tags) where docker images are pushed.