Add README.md to typescript init templates

Those files provide useful commands that will be displayed in the
terminal after a successful run of `cdk init`.

packages/aws-cdk/lib/init-templates/app/cdk.json

@@ -0,0 +1,3 @@
+{
+    "app": "node bin/%name%.js"
+}

packages/aws-cdk/lib/init-templates/app/typescript/README.md

@@ -0,0 +1,11 @@
+# Useful commands
+```shell
+npm run prepare # Compile the source code
+npm run watch # Watch for file changes and compile automatically
+
+cdk synth # See the CloudFormation template for this app
+cdk diff # See the differences between this app and what is deployed
+cdk deploy # Deploy this app to your AWS account
+
+cdk-beta-npm install # Install new CDK dependencies
+```

packages/aws-cdk/lib/init-templates/lib/typescript/README.md

@@ -0,0 +1,7 @@
+# Useful commands
+```shell
+npm run prepare # Compile the source code
+npm run watch # Watch for file changes and compile automatically
+
+cdk-beta-npm install # Install new CDK dependencies
+```

packages/aws-cdk/lib/init.ts

@@ -195,9 +195,6 @@ async function postInstallTypescript() {
     if (await execCdkBetaNpm('install') !== 0) {
         throw new Error('cdk-beta-npm install failed!');
     }
-    print(`Use ${colors.blue('cdk synth')} to see the generated CloudFormation template`);
-    print(`Use ${colors.blue('cdk deploy')} to deploy the application to CloudFormation`);
-    print(`Use ${colors.blue('cdk-beta-npm install')} instead of ${colors.blue('npm install')}`);
 }
 
 /**