Add Tokyo Special Wards

[HarukiKinoshita]

Inspired by London-Boroughs, I created the map of Tokyo special wards.

[VictorCazanave]

Thanks a lot for your contribution! 😃

I'm still thinking about how to deal with the maps other than countries (i.e. cities, counties, states...) because I'm worried this repository will become too messy. Then I'll review it, when I take a decision (I'm open to suggestions).

[HarukiKinoshita]

That makes sense! Would be better to keep it simple 👍