build(deps): upgrade webpack version to ^4.36.0

Webpack 4.36.0 is the minimum version that sass-loader 8 requires.

- 4.20.0 has been released september 2018: https://github.com/webpack/webpack/releases/tag/v4.20.0
- 4.36.0 has been released in july 2019: https://github.com/webpack/webpack/releases/tag/v4.36.0

Author: Kocal

package.json

@@ -46,7 +46,7 @@
     "style-loader": "^1.1.3",
     "terser-webpack-plugin": "^1.1.0",
     "tmp": "^0.0.33",
-    "webpack": "^4.20.0",
+    "webpack": "^4.36.0",
     "webpack-cli": "^3.0.0",
     "webpack-dev-server": "^3.1.14",
     "webpack-manifest-plugin": "^2.0.2",

yarn.lock

@@ -8758,7 +8758,7 @@ webpack-sources@^1.1.0, webpack-sources@^1.3.0, webpack-sources@^1.4.0, webpack-
     source-list-map "^2.0.0"
     source-map "~0.6.1"
 
-webpack@^4.20.0:
+webpack@^4.36.0:
   version "4.42.1"
   resolved "https://registry.yarnpkg.com/webpack/-/webpack-4.42.1.tgz#ae707baf091f5ca3ef9c38b884287cfe8f1983ef"
   integrity sha512-SGfYMigqEfdGchGhFFJ9KyRpQKnipvEvjc1TwrXEPCM6H5Wywu10ka8o3KGrMzSMxMQKt8aCHUFh5DaQ9UmyRg==