Set webpack-dev-server host to 0.0.0.0 (#1122)

webpack-dev-server CLI has a default value of localhost, which only
allows accessing locally. Setting to 0.0.0.0 allows to access the server
from the external. However, the open option will open 0.0.0.0:7936,
which is an invalid address, so it has been removed.

package.json

@@ -64,7 +64,7 @@
     "clean-install": "npm run clean && npm i",
     "test": "check-dependencies && npm run lint && npm run flow && npm run jest",
     "verify-screenshots": "check-dependencies && dockers/Screenshotter/screenshotter.sh --verify",
-    "start": "check-dependencies && webpack-dev-server --open --config webpack.dev.js",
+    "start": "check-dependencies && webpack-dev-server --config webpack.dev.js",
     "build": "check-dependencies && rimraf build/* && webpack",
     "watch": "npm run build -- --watch",
     "perf-test": "check-dependencies && NODE_ENV=test node test/perf-test.js",

webpack.dev.js

@@ -13,6 +13,7 @@ katexConfig.devServer = {
     // testing.  This potentially reveals the source code to the world,
     // but this should not be a concern for testing open-source software.
     disableHostCheck: true,
+    host: '0.0.0.0',
     port: PORT,
     stats: {
         colors: true,