add addMark command

packages/core/src/commands/addMark.ts

@@ -0,0 +1,15 @@
+import { MarkType } from 'prosemirror-model'
+import { Command } from '../types'
+import getMarkType from '../utils/getMarkType'
+
+export default (typeOrName: string | MarkType, attributes?: {}): Command => ({ tr, state, dispatch }) => {
+  const { selection } = tr
+  const type = getMarkType(typeOrName, state.schema)
+  const { from, to } = selection
+
+  if (dispatch) {
+    tr.addMark(from, to, type.create(attributes))
+  }
+
+  return true
+}