Only few reserved country codes missing

[RudeySH]

I noticed this project contains a bunch of reserved country codes (see the Exceptional reservations section).

This repository contains flags for AC, CP, DG, EA, EU, IC, TA and UN. These are almost all reserved country codes, only a few are missing.

For example, the flag for the UK country code, which is listed on Wikipedia, is not in this repository. The same goes for SU.

For the sake of completeness I think these missing flags should be added.