Add Open Containers annotations to Docker image

packaging/docker/Dockerfile

@@ -9,8 +9,18 @@ RUN go build \
     main.go
 
 FROM alpine:latest
+
+LABEL org.opencontainers.image.title=Miniflux
+LABEL org.opencontainers.image.description="Miniflux is a minimalist and opinionated feed reader"
+LABEL org.opencontainers.image.vendor="Frédéric Guillot"
+LABEL org.opencontainers.image.licenses=Apache-2.0
+LABEL org.opencontainers.image.url=https://miniflux.app
+LABEL org.opencontainers.image.source=https://github.com/miniflux/v2
+LABEL org.opencontainers.image.documentation=https://miniflux.app/docs/
+
 EXPOSE 8080
 ENV LISTEN_ADDR 0.0.0.0:8080
+
 RUN apk --no-cache add ca-certificates tzdata
 COPY --from=build /go/src/app/miniflux /usr/bin/miniflux
 USER nobody