chore: import upstream snapshot with attribution

tools/challenge-parser/parser/plugins/utils/get-section.js

@@ -0,0 +1,58 @@
+const find = require('unist-util-find');
+const findAfter = require('unist-util-find-after');
+const findAllAfter = require('unist-util-find-all-after');
+const between = require('unist-util-find-all-between');
+const { findAll } = require('./find-all');
+
+const isMarker = node => {
+  if (node.children && node.children[0]) {
+    const child = node.children[0];
+    return (
+      child.type === 'text' &&
+      child.value.startsWith('--') &&
+      child.value.endsWith('--') &&
+      node.type === 'heading'
+    );
+  }
+  return false;
+};
+
+function _getSection(tree) {
+  return start => {
+    if (!start) return [];
+
+    const isEnd = node => {
+      return node.depth <= start.depth && isMarker(node);
+    };
+
+    const end = findAfter(tree, start, isEnd);
+
+    const targetNodes = end
+      ? between(tree, start, end)
+      : findAllAfter(tree, start);
+    return targetNodes;
+  };
+}
+
+const startNode = (marker, depth) => ({
+  type: 'heading',
+  children: [
+    {
+      type: 'text',
+      value: marker
+    }
+  ],
+  ...((typeof depth === 'number' && { depth }) || {})
+});
+
+function getSection(tree, marker, depth) {
+  const start = find(tree, startNode(marker, depth));
+  return _getSection(tree)(start);
+}
+
+function getAllSections(tree, marker) {
+  const starts = findAll(tree, startNode(marker));
+  return starts.map(_getSection(tree));
+}
+
+module.exports = { getSection, getAllSections, isMarker };