chore: import upstream snapshot with attribution

tools/challenge-parser/parser/plugins/utils/before-heading.js

@@ -0,0 +1,21 @@
+const find = require('unist-util-find');
+const findAllBefore = require('unist-util-find-all-before');
+
+function getAllBefore(tree, marker) {
+  const start = find(tree, {
+    type: 'heading',
+    children: [
+      {
+        type: 'text',
+        value: marker
+      }
+    ]
+  });
+
+  if (!start) return [];
+
+  // reverse because it goes up the tree backwards and adds nodes in that order
+  return findAllBefore(tree, start).reverse();
+}
+
+module.exports = getAllBefore;