Add Kosovo (XK) and Western Sahara (EH) to the country list. Kosovo
has no Unicode emoji flag, so it follows the Tibet pattern with a
bundled SVG asset that CountryFlag swaps in.
Surface Tibet (CN-XZ) as a search-list entry so it can be picked from
country autocompletes and pickers. The on-wire identifier stays
iso3166:CN-XZ; only the picker pretends.
Route every remaining raw country.flag span through CountryFlag so
bundled SVGs render in autocomplete dropdowns, organizer selects, the
ComposeBox destination switcher, and the world stats dialog.
Chad Curtis
