Update monaco-editor-core to 0.28.1

package.json

@@ -23,7 +23,7 @@
     "event-stream": "4.0.1",
     "gulp": "^4.0.2",
     "monaco-css": "3.7.0",
-    "monaco-editor-core": "0.28.0",
+    "monaco-editor-core": "0.28.1",
     "monaco-html": "3.7.0",
     "monaco-json": "3.7.0",
     "monaco-languages": "2.7.0",