add docker manifest

Dockerfile

@@ -0,0 +1,19 @@
+FROM golang AS build
+
+ARG GIT_DESC=undefined
+
+WORKDIR /go/src/github.com/Snawoot/opera-proxy
+COPY . .
+RUN CGO_ENABLED=0 go build -a -tags netgo -ldflags '-s -w -extldflags "-static" -X main.version='"$GIT_DESC"
+ADD https://curl.haxx.se/ca/cacert.pem /certs.crt
+RUN chmod 0644 /certs.crt
+
+FROM scratch AS arrange
+COPY --from=build /go/src/github.com/Snawoot/opera-proxy/opera-proxy /
+COPY --from=build /certs.crt /etc/ssl/certs/ca-certificates.crt
+
+FROM scratch
+COPY --from=arrange / /
+USER 9999:9999
+EXPOSE 8080/tcp
+ENTRYPOINT ["/opera-proxy", "-bind-address", "0.0.0.0:18080"]