Upgrade webpacker to fix security dependency

- Also update github actions file inline with the comment on the GithubActions for Yarn:
https://github.com/marketplace/actions/github-action-for-yarn

```
Please keep in mind that this Action was originally written for GitHub Actions beta (when Docker was the only way of doing things).
Consider using actions/setup-node to work with Yarn.
This repository will be mostly supporting the existing flows.
```

Author: melzreal

.github/workflows/build.yml

@@ -20,10 +20,11 @@ jobs:
       with:
         postgresql version: '11'
 
-    - name: Install Yarn
-      uses: borales/actions-yarn@v2.0.0
+    - name: Install Node
+      uses: actions/setup-node@v2
       with:
-        cmd: install
+        node-version: '14'
+    - run: yarn install
 
     - name: Install file previewing tools
       run: |

Gemfile

@@ -25,7 +25,7 @@ gem "pg", ">= 0.18", "< 2.0"
 gem "puma", "~> 4.1"
 gem "rails", "~> 6.1.3"
 gem "rswag-ui"
-gem "webpacker", "~> 4.0"
+gem "webpacker", "~> 5.2", ">= 5.2.1"
 
 group :development, :test do
   gem "brakeman", require: false

Gemfile.lock

@@ -322,6 +322,7 @@ GEM
     selenium-webdriver (3.142.7)
       childprocess (>= 0.5, < 4.0)
       rubyzip (>= 1.2.2)
+    semantic_range (3.0.0)
     simplecov (0.21.2)
       docile (~> 1.1)
       simplecov-html (~> 0.11)
@@ -350,10 +351,11 @@ GEM
       addressable (>= 2.3.6)
       crack (>= 0.3.2)
       hashdiff (>= 0.4.0, < 2.0.0)
-    webpacker (4.3.0)
-      activesupport (>= 4.2)
+    webpacker (5.2.1)
+      activesupport (>= 5.2)
       rack-proxy (>= 0.6.1)
-      railties (>= 4.2)
+      railties (>= 5.2)
+      semantic_range (>= 2.3.0)
     websocket-driver (0.7.3)
       websocket-extensions (>= 0.1.0)
     websocket-extensions (0.1.5)
@@ -405,7 +407,7 @@ DEPENDENCIES
   simplecov
   web-console (>= 3.3.0)
   webmock
-  webpacker (~> 4.0)
+  webpacker (~> 5.2, >= 5.2.1)
 
 BUNDLED WITH
    2.2.7

babel.config.js

@@ -56,9 +56,7 @@ module.exports = function(api) {
       [
         '@babel/plugin-transform-runtime',
         {
-          helpers: false,
-          regenerator: true,
-          corejs: false
+          helpers: false
         }
       ],
       [

config/webpack/environment.js

@@ -1,19 +1,3 @@
 const { environment } = require('@rails/webpacker')
-const { merge } = require('webpack-merge')
-
-const sassLoader = environment.loaders.get('sass')
-const cssLoader = environment.loaders.get('css')
-
-sassLoader.use.map(function(loader) {
-  if (loader.options) {
-    loader.options = merge(loader.options, { sourceMap: false })
-  }
-});
-
-cssLoader.use.map(function(loader) {
-  if (loader.options) {
-    loader.options = merge(loader.options, { sourceMap: false })
-  }
-});
 
 module.exports = environment

config/webpacker.yml

@@ -6,12 +6,11 @@ default: &default
   public_root_path: public
   public_output_path: packs
   cache_path: tmp/cache/webpacker
-  check_yarn_integrity: false
   webpack_compile_output: true
 
   # Additional paths webpack should lookup modules
   # ['app/assets', 'engine/foo/app/assets']
-  resolved_paths: []
+  additional_paths: []
 
   # Reload manifest.json on all requests so we reload latest compiled packs
   cache_manifest: false
@@ -51,10 +50,6 @@ default: &default
 development:
   <<: *default
   compile: true
-  extract_css: true
-
-  # Verifies that correct packages and versions are installed by inspecting package.json, yarn.lock, and node_modules
-  check_yarn_integrity: false
 
   # Reference: https://webpack.js.org/configuration/dev-server/
   dev_server:

package.json

@@ -4,14 +4,15 @@
   "dependencies": {
     "@rails/activestorage": "^6.0.0",
     "@rails/ujs": "^6.0.0",
-    "@rails/webpacker": "^4.2.2",
+    "@rails/webpacker": "5.2.1",
     "govuk-frontend": "^3.6.0",
     "stimulus": "^1.1.1",
     "toastr": "^2.1.4",
+    "webpack": "^4.0.0",
     "webpack-merge": "^5.4.0"
   },
   "version": "0.1.0",
   "devDependencies": {
-    "webpack-dev-server": "^3.10.3"
+    "webpack-dev-server": "^3.11.2"
   }
 }