update rocket_prometheus to 0.10.1

update rocket to 0.5.0

update to rust 1.73

update cargo dependencies

update to rust 1.63

update container base image to rust:1.62-alpine

update cargo dependencies

switch from niv to npins

pin rust version for the docker build

set up cachix cache for nixos builds

install rustup using apk

reformat build yaml files

update crates and niv dependencies

use package name and version from Cargo.toml

ignore git files/directories in src

add a readme with some useful docker commands

add a Dockerfile for an alpine based image

add docker-image ci.nix target

add ci.nix for building the rust-hello-world release

add /metrics endpoint with prometheus metrics