Revert part of PR "remove references to mapbox key, which we are no longer using"

Author: CodeWritingCow

src/config/config.ts

@@ -1,5 +1,9 @@
 const EMPTY_STRING = '';
 
+export const mapboxAccessToken =
+  'pk.eyJ1IjoibmxlYm92aXRzIiwiYSI6ImNsZXQ2Nzd3ZDBjZnYzcHFvYXhib2RqYzQifQ.PWg2LuNCH1E6-REjmYvdOg' ||
+  EMPTY_STRING;
+
 export const maptilerApiKey =
   process.env.NEXT_PUBLIC_MAPTILER_KEY || EMPTY_STRING;