Better docker for the frontend (#240)

* Exclude vscode local settings

* Switch the image to nginx with ENV support

* Add some doc

* Fix travis config

* Ignore coverage data

* Remove version labels

* Fix the Dockerfile according to the recent refactoring

* Cleanup

* Change maintainer

According to @woss request

* Fix travis config

frontend/Dockerfile

@@ -0,0 +1,31 @@
+#### BUILDER IMAGE  ####
+FROM node:12 as builder
+LABEL maintainer="Chevdor <chevdor@gmail.com>"
+LABEL description="Polkadot Telemetry frontend builder image"
+
+WORKDIR /opt/builder
+
+COPY . .
+RUN yarn install && \
+    yarn build && \
+    yarn cache clean
+
+
+#### OUTPUT IMAGE ####
+FROM nginx:stable-alpine
+LABEL maintainer="Chevdor <chevdor@gmail.com>"
+LABEL description="Polkadot Telemetry frontend"
+
+ENV SUBSTRATE_TELEMETRY_URL=
+
+WORKDIR /usr/share/nginx/html
+
+COPY --from=builder /opt/builder/env.sh /usr/bin/
+RUN apk add --no-cache bash; chmod +x /usr/bin/env.sh
+
+COPY --from=builder /opt/builder/nginx/nginx.conf /etc/nginx/nginx.conf
+COPY --from=builder /opt/builder/build /usr/share/nginx/html
+
+EXPOSE 80
+
+CMD ["/bin/bash", "-c", "/usr/bin/env.sh && nginx -g \"daemon off;\""]