Allow HTML comments containing "--" even though it is not allowed by the CommonMark specification because it is allowed by the HTML specification and it happens in real life (fixes #996).

test/front-matter-yaml-in-html-comment.md

@@ -0,0 +1,14 @@
+<!--
+---
+title: Front Matter YAML in HTML Comment
+not-md035: |-
+  ***
+  * * *
+description: |-
+  This document has YAML front matter inside an HTML comment.
+---
+-->
+
+# Front Matter YAML in HTML Comment
+
+Text text text

test/snapshots/markdownlint-test-scenarios.js.md

@@ -13866,6 +13866,29 @@ Generated by [AVA](https://avajs.dev).
       `,
     }
 
+## front-matter-yaml-in-html-comment.md
+
+> Snapshot 1
+
+    {
+      errors: [],
+      fixed: `<!--␊
+      ---␊
+      title: Front Matter YAML in HTML Comment␊
+      not-md035: |-␊
+        ***␊
+        * * *␊
+      description: |-␊
+        This document has YAML front matter inside an HTML comment.␊
+      ---␊
+      -->␊
+      ␊
+      # Front Matter YAML in HTML Comment␊
+      ␊
+      Text text text␊
+      `,
+    }
+
 ## front-matter.md
 
 > Snapshot 1