fix(aws-cdk): fix ts-node usage on Windows (#2660)

Fix an error when running any cdk command on Windows caused by '/' in ts-node path.

Author: Iamz

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

@@ -1,3 +1,3 @@
 {
-  "app": "./node_modules/.bin/ts-node bin/%name%.ts"
+  "app": "npx ts-node bin/%name%.ts"
 }

packages/aws-cdk/lib/init-templates/sample-app/typescript/cdk.template.json

@@ -1,3 +1,3 @@
 {
-  "app": "./node_modules/.bin/ts-node bin/%name%.ts"
+  "app": "npx ts-node bin/%name%.ts"
 }