Add empty TypeScript starter template file. Closes #279

No content, the header with the same CTA as in site.js

And no BOM, there is no policy to enforce it in the repo.

Thanks!

src/Microsoft.DotNet.Web.Client.ItemTemplates/content/TypeScript/file1.ts

@@ -1,2 +1 @@
-body {
-}
+// Write your TypeScript code.