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/env.sh

@@ -0,0 +1,20 @@
+#!/bin/bash
+
+# This script is used when the docker container starts and does the magic to
+# bring the ENV variables to the generated static UI.
+
+TARGET=./env-config.js
+
+# Recreate config file
+echo -n > $TARGET
+
+declare -a vars=(
+  "SUBSTRATE_TELEMETRY_URL"
+  "SUBSTRATE_TELEMETRY_SAMPLE"
+)
+
+echo "window.process_env = {" >> $TARGET
+for VAR in ${vars[@]}; do
+  echo "  $VAR: \"${!VAR}\"," >> $TARGET
+done
+echo "}" >> $TARGET