Add a tutorial for using TypeScript in an addon #303
Description
Similar to https://cli.emberjs.com/release/writing-addons/intro-tutorial/, we could teach how to use TypeScript in an addon.
This work was proposed in typed-ember/ember-cli-typescript#1422 and that issue includes draft outline content.
@alankyshum are you interested in adding this? If not, is it alright for us to use what you have already written?