[Tagging] Add tags to a taxonomy

[bradenmacdonald]

TODO

[ali-hugo]

@bradenmacdonald The UX for adding tags has been finalised. Please take a look at the user flow here and let me know if you have any questions.

[bradenmacdonald]

@ali-hugo We are holding off on all the editing features (milestone 4) for now, but will be getting to them after the current milestone and user testing.