feat: Create .browserslistrc file when user chose "separate config files" (#1773)

* feat(cli): When selecting "separate config files",
cli should create .browserslistrc file

close #1236

* test(cli): add test for extracting .browserslistrc

Author: LinusBorg

packages/@vue/cli/__tests__/Generator.spec.js

@@ -473,7 +473,11 @@ test('extract config files', async () => {
     },
     jest: {
       foo: 'bar'
-    }
+    },
+    browserslist: [
+      '> 1%',
+      'not <= IE8'
+    ]
   }
 
   const generator = new Generator('/', { plugins: [
@@ -495,4 +499,5 @@ test('extract config files', async () => {
   expect(fs.readFileSync('/.postcssrc.js', 'utf-8')).toMatch(js(configs.postcss))
   expect(fs.readFileSync('/.eslintrc.js', 'utf-8')).toMatch(js(configs.eslintConfig))
   expect(fs.readFileSync('/jest.config.js', 'utf-8')).toMatch(js(configs.jest))
+  expect(fs.readFileSync('/.browserslistrc', 'utf-8')).toMatch('> 1%\nnot <= IE8')
 })

packages/@vue/cli/lib/util/configTransforms.js

@@ -94,10 +94,18 @@ function transformYAML (value, filename, source) {
   }
 }
 
+function transformBrowserslist (value, filename, source) {
+  return {
+    filename: `.browserslistrc`,
+    content: value.join('\n')
+  }
+}
+
 module.exports = {
   vue: makeJSTransform('vue.config.js'),
   babel: makeJSTransform('babel.config.js'),
   postcss: makeMutliExtensionJSONTransform('.postcssrc', true),
   eslintConfig: makeMutliExtensionJSONTransform('.eslintrc', true),
-  jest: makeJSTransform('jest.config.js')
+  jest: makeJSTransform('jest.config.js'),
+  browserslist: transformBrowserslist
 }