Add Toki Pona to languages

Would like to add this language not because it is widely spoken (there are not a super large number of labels in this language in OSM (though many more on Wikidata)) but because I want to make a website with a map in it.

openmaptiles.yaml

@@ -98,6 +98,7 @@ tileset:
     - ta # Tamil
     - te # Telugu
     - th # Thai
+    - tok # Toki Pona
     - tr # Turkish, Latin
     - uk # Ukrainian
     - ur # Urdu