style: move node text content into helper function

packages/core/src/helpers/getTextContentFromNodes.ts

@@ -0,0 +1,17 @@
+import { ResolvedPos } from 'prosemirror-model'
+
+export const getTextContentFromNodes = ($from: ResolvedPos<any>, maxMatch = 500) => {
+  let textBefore = ''
+
+  $from.parent.nodesBetween(
+    Math.max(0, $from.parentOffset - maxMatch),
+    $from.parentOffset,
+    (node, pos, parent, index) => {
+      textBefore += node.type.spec.toText?.({
+        node, pos, parent, index,
+      }) || node.textContent || '%leaf%'
+    },
+  )
+
+  return textBefore
+}