Add collectCoverageFrom option to collect coverage on files without any tests. (#961)

Author: mackbyte

packages/react-scripts/utils/createJestConfig.js

@@ -18,6 +18,7 @@ module.exports = (resolve, rootDir, isEjecting) => {
   const setupTestsFile = pathExists.sync(paths.testsSetup) ? '<rootDir>/src/setupTests.js' : undefined;
 
   const config = {
+    collectCoverageFrom: ['src/**/*.{js,jsx}'],
     moduleFileExtensions: ['jsx', 'js', 'json'],
     moduleNameMapper: {
       '^.+\\.(jpg|jpeg|png|gif|eot|otf|webp|svg|ttf|woff|woff2|mp4|webm|wav|mp3|m4a|aac|oga)$': resolve('config/jest/FileStub.js'),