Bump webpack from 4.30.0 to 4.31.0 in /js

Bumps [webpack](https://github.com/webpack/webpack) from 4.30.0 to 4.31.0.
- [Release notes](https://github.com/webpack/webpack/releases)
- [Commits](https://github.com/webpack/webpack/compare/v4.30.0...v4.31.0)

Signed-off-by: dependabot[bot] <support@dependabot.com>

js/package-lock.json

@@ -1762,11 +1762,12 @@
       }
     },
     "assert": {
-      "version": "1.4.1",
-      "resolved": "https://registry.npmjs.org/assert/-/assert-1.4.1.tgz",
-      "integrity": "sha1-mZEtWRg2tab1s0XA8H7vwI/GXZE=",
+      "version": "1.5.0",
+      "resolved": "https://registry.npmjs.org/assert/-/assert-1.5.0.tgz",
+      "integrity": "sha512-EDsgawzwoun2CZkCgtxJbv392v4nbk9XDD06zI+kQYoBM/3RBWLlEyJARDOmhAAosBjWACEkKL6S+lIZtcAubA==",
       "dev": true,
       "requires": {
+        "object-assign": "^4.1.1",
         "util": "0.10.3"
       },
       "dependencies": {
@@ -7451,9 +7452,9 @@
       }
     },
     "webpack": {
-      "version": "4.30.0",
-      "resolved": "https://registry.npmjs.org/webpack/-/webpack-4.30.0.tgz",
-      "integrity": "sha512-4hgvO2YbAFUhyTdlR4FNyt2+YaYBYHavyzjCMbZzgglo02rlKi/pcsEzwCuCpsn1ryzIl1cq/u8ArIKu8JBYMg==",
+      "version": "4.31.0",
+      "resolved": "https://registry.npmjs.org/webpack/-/webpack-4.31.0.tgz",
+      "integrity": "sha512-n6RVO3X0LbbipoE62akME9K/JI7qYrwwufs20VvgNNpqUoH4860KkaxJTbGq5bgkVZF9FqyyTG/0WPLH3PVNJA==",
       "dev": true,
       "requires": {
         "@webassemblyjs/ast": "1.8.5",

js/package.json

@@ -40,7 +40,7 @@
     "vue-loader": "^15.7.0",
     "vue-style-loader": "^4.1.2",
     "vue-template-compiler": "^2.6.10",
-    "webpack": "^4.30.0",
+    "webpack": "^4.31.0",
     "webpack-cli": "^3.3.2",
     "webpack-merge": "^4.2.1"
   },