Create a Typescript variation for the create-block script

[stevenslack]

Using the create-block script we should be able to create a variation where .ts and .tsx files are generated from the bin/create-block script. The mustache files should be able to support a TS version.

[stevenslack]

Details for external templates can be found here: https://github.com/WordPress/gutenberg/blob/trunk/packages/create-block/docs/external-template.md