Add TypeScript types for the addon components and helpers

[Panman82]

Apparently there is a types file that can be added to help with TypeScript support. Probably worth adding since the ember community is moving that direction.

typed-ember/ember-cli-typescript#48

[Panman82]

Just to add here, there is an open issue on the main editor repo (upstream from this Ember addon) requesting that TypeScript definitions be added: froala/wysiwyg-editor#2369

[Panman82]

Once this addon moves to embroider (addon v2) format, the actual components/helpers/etc. will move to "native" TypeScript files with all the types needed.

[Panman82]

Just to note, there is apparently upstream types available now, but I haven't looked into them yet: froala/wysiwyg-editor#2369