docker: Use multi-stage docker builds

Signed-off-by: Gunwant Jain <mail@wantguns.dev>

Dockerfile

@@ -1,17 +1,20 @@
 FROM rust:1 as builder
 WORKDIR /app
 COPY . .
-
-RUN cargo install --path .
+RUN RUSTFLAGS='-C target-feature=+crt-static' cargo install --target x86_64-unknown-linux-gnu --path .
 RUN cargo clean
 
+FROM debian:buster-slim as runner
+WORKDIR /app
 RUN mkdir -p upload
 COPY ./client upload/client
 COPY ./templates templates
 COPY ./static static
+COPY ./themes themes
+COPY --from=builder /usr/local/cargo/bin/bin .
 
 ENV ROCKET_ADDRESS=0.0.0.0
 ENV ROCKET_PORT=6162
 
 EXPOSE 6162
-CMD ["bin"]
+CMD ["./bin"]