Reimplement MD028/no-blanks-blockquote using micromark tokens.

helpers/micromark.cjs

@@ -295,6 +295,28 @@ function filterByTypes(tokens, types) {
   return filterByPredicate(tokens, predicate);
 }
 
+/**
+ * Gets all sibling token groups for a list of Micromark tokens.
+ *
+ * @param {Token[]} tokens Micromark tokens.
+ * @returns {Token[][]} Sibling token groups.
+ */
+function getSiblingTokens(tokens) {
+  const result = [];
+  const queue = [ tokens ];
+  // eslint-disable-next-line init-declarations
+  let current;
+  while ((current = queue.shift())) {
+    result.push(current);
+    for (const token of current) {
+      if (token.children.length > 0) {
+        queue.push(token.children);
+      }
+    }
+  }
+  return result;
+}
+
 /**
  * Gets the heading level of a Micromark heading tokan.
  *
@@ -419,6 +441,7 @@ module.exports = {
   getHeadingLevel,
   getHtmlTagInfo,
   getMicromarkEvents,
+  getSiblingLists: getSiblingTokens,
   getTokenParentOfType,
   getTokenTextByType,
   inHtmlFlow,