Added docker building.

Dockerfile

@@ -4,6 +4,7 @@ WORKDIR /app
 COPY Cargo.toml Cargo.lock askama.toml ./
 COPY src ./src
 COPY static ./static
+# Build binary in release mode.
 RUN cargo build --release --all-features
 
 FROM debian:bullseye-20230109-slim as base
@@ -16,12 +17,16 @@ RUN apt-get update \
 
 COPY static ./static
 
+# Copy built binary to a new image.
 COPY --from=builder /app/target/release/s3bot /usr/local/bin/
 
 ENTRYPOINT ["/usr/local/bin/s3bot"]
 
 FROM base as rootless
 
+# Create a user and make the image rootless. So no one
+# can escalate privileges even if they have access to
+# container.
 RUN useradd --create-home  -u 1000 --user-group s3bot
 WORKDIR /home/s3bot
 RUN mv /static ./static