Add Ascension Island and Tristan da Cunha data

[LKay]

Both of these are overseas territories with their own respective phone calling codes and ISO reserved codes.

Data changes verified with:

Ascension Island:

• https://en.wikipedia.org/wiki/Ascension_Island
• https://www.iso.org/obp/ui/#iso:code:3166:AC

Tristan da Cunha:

• https://en.wikipedia.org/wiki/Tristan_da_Cunha
• https://www.iso.org/obp/ui/#iso:code:3166:TA

[dmythro]

Thanks for the update, looks good! Will check and release this a bit later when get back.