Add TypeScript app creation (#5550)

* Add TypeScript app creation

* Actually specify new extension

* Check for ts and tsx

* Fix types in default service worker file

* Mirror changes in JS version of SW

* Separate templates

* Use separate template directory

* Remove unused function

* Add a tsconfig file to the template

* Test install of typescript

* Add e2e for TypeScript

* Check for index.tsx to make sure we're not in the JS template

* Ensure TypeScript doesn't leak into normal installs

* Ignore some files

* Print version of CRA

* Fix script

* Add new template

* Move test to correct location

* Use `verifyTypeScriptSetup` routine to populate files

* Ensure tsconfig is created

packages/react-scripts/scripts/init.js

@@ -21,6 +21,7 @@ const execSync = require('child_process').execSync;
 const spawn = require('react-dev-utils/crossSpawn');
 const { defaultBrowsers } = require('react-dev-utils/browsersHelper');
 const os = require('os');
+const verifyTypeScriptSetup = require('./utils/verifyTypeScriptSetup');
 
 function isInGitRepository() {
   try {
@@ -90,6 +91,8 @@ module.exports = function(
   // Copy over some of the devDependencies
   appPackage.dependencies = appPackage.dependencies || {};
 
+  const useTypeScript = appPackage.dependencies['typescript'] != null;
+
   // Setup the script rules
   appPackage.scripts = {
     start: 'react-scripts start',
@@ -122,7 +125,7 @@ module.exports = function(
   // Copy the files for the user
   const templatePath = template
     ? path.resolve(originalDirectory, template)
-    : path.join(ownPath, 'template');
+    : path.join(ownPath, useTypeScript ? 'template-typescript' : 'template');
   if (fs.existsSync(templatePath)) {
     fs.copySync(templatePath, appPath);
   } else {
@@ -192,6 +195,10 @@ module.exports = function(
     }
   }
 
+  if (useTypeScript) {
+    verifyTypeScriptSetup();
+  }
+
   if (tryGitInit(appPath)) {
     console.log();
     console.log('Initialized a git repository.');