Move build script to a yarn command, prettify JSON output.

.travis.yml

@@ -18,7 +18,7 @@ install:
   - bundle install
   - nvm install 9
   - nvm use 9
-  - yarn install
+  - yarn install --frozen-lockfile
   - yarn list
 before_script:
   - cp config/database.yml.travis config/database.yml
@@ -28,7 +28,7 @@ script:
   - bundle exec rake db:seed
   - bundle exec rake test
   - bundle exec rake test:system
-  - node lib/build.js
+  - yarn run build
   - git diff --exit-code --quiet public/data.json
   - bundle exec rake check:check_mdn_bcd_version 
   - bundle exec rake check:check_json 

lib/build.js

@@ -37,7 +37,7 @@ fs.writeFile(
     'public',
     'data.json'
   ),
-  JSON.stringify(payload),
+  JSON.stringify(payload, null, 2),
   err => {
     if (err) {
       console.error(err)

lib/tasks/update.rake

@@ -62,9 +62,9 @@ namespace :update do
     puts "Continuing..."
 
     puts ""
-    puts "Regenerating 'public/data.json' with 'node lib/build.js'."
-    puts "node lib/build.js"
-    system('node lib/build.js') or exit
+    puts "Regenerating 'public/data.json' with 'yarn run build'."
+    puts "yarn run build"
+    system('yarn run build') or exit
     puts "Continuing..."
 
     puts ""

package.json

@@ -4,5 +4,8 @@
   "dependencies": {
     "chart.js": "^2.7.2",
     "mdn-browser-compat-data": "0.0.39"
+  },
+  "scripts": {
+    "build": "node ./lib/build.js"
   }
 }