all these changes

frontend/node_modules/core-js/modules/esnext.map.upsert.js

@@ -0,0 +1,10 @@
+'use strict';
+// TODO: remove from `core-js@4`
+var $ = require('../internals/export');
+var upsert = require('../internals/map-upsert');
+
+// `Map.prototype.upsert` method (replaced by `Map.prototype.emplace`)
+// https://github.com/thumbsupep/proposal-upsert
+$({ target: 'Map', proto: true, real: true, forced: true }, {
+  upsert: upsert
+});