Upgrade Webpacker to version 3.0.1 (#5122)

config/webpacker.yml

@@ -4,6 +4,15 @@ default: &default
   source_path: app/javascript
   source_entry_path: packs
   public_output_path: packs
+  cache_path: tmp/cache/webpacker
+
+  # Additional paths webpack should lookup modules
+  # ['app/assets', 'engine/foo/app/assets']
+  resolved_paths: []
+
+  # Reload manifest.json on all requests so we reload latest compiled packs
+  cache_manifest: false
+
   extensions:
     - .js
     - .sass
@@ -17,16 +26,25 @@ default: &default
 
 development:
   <<: *default
+  compile: true
 
   dev_server:
-    host: 127.0.0.1
-    port: 8080
+    host: localhost
+    port: 3035
+    hmr: false
     https: false
 
 test:
   <<: *default
 
+  # Compile test packs to a separate directory
   public_output_path: packs-test
 
 production:
   <<: *default
+
+  # Production depends on precompilation of packs prior to booting for performance.
+  compile: false
+
+  # Cache manifest.json for performance
+  cache_manifest: true