add toggleMark command

packages/core/src/utils/getMarkType.ts

@@ -0,0 +1,9 @@
+import { MarkType, Schema } from 'prosemirror-model'
+
+export default function getMarkType(nameOrType: string | MarkType, schema: Schema): MarkType {
+  if (typeof nameOrType === 'string') {
+    return schema.marks[nameOrType]
+  }
+
+  return nameOrType
+}