feat(packages/sui-polyfills): add FlatMap polyfill

Author: Alisa Bayanova

packages/sui-polyfills/src/index.js

@@ -2,6 +2,7 @@ require('core-js/features/array/fill')
 require('core-js/features/array/find-index')
 require('core-js/features/array/find')
 require('core-js/features/array/flat')
+require('core-js/features/array/flat-map')
 require('core-js/features/array/from')
 require('core-js/features/array/includes')
 require('core-js/features/array/is-array')