Chore(docker): update Dockerfile (#87)

Dockerfile

@@ -7,6 +7,7 @@ RUN apk add --update --no-cache --no-progress make git \
     && make server
 
 FROM alpine:latest
+LABEL org.opencontainers.image.licenses=Apache-2.0
 LABEL org.opencontainers.image.source="https://github.com/metatube-community/metatube-sdk-go"
 
 COPY --from=builder /src/build/metatube-server .
@@ -23,4 +24,6 @@ ENV DB_MAX_OPEN_CONNS=0
 ENV DB_PREPARED_STMT=0
 ENV DB_AUTO_MIGRATE=0
 
+EXPOSE 8080
+
 ENTRYPOINT ["/metatube-server"]