Add a Dockerfile for building a container image (#8)

* Add a Dockerfile

* Reduce image size from ~75MB to ~6MB

* Add Dockerignore and README documentation

* Add Docker build action to CI

Co-authored-by: Eric Zhang <ekzhang1@gmail.com>

Dockerfile

@@ -0,0 +1,10 @@
+FROM rust:alpine as builder
+WORKDIR /home/rust/src
+RUN apk --no-cache add musl-dev
+COPY . .
+RUN cargo install --path .
+
+FROM scratch
+COPY --from=builder /usr/local/cargo/bin/bore .
+USER 1000:1000
+ENTRYPOINT ["./bore"]