Support Speculation Rules API formatting in HTML (#12882)

* Add script formatting for `speculationrules`

* Fix lint problems

tests/format/html/script/script.html

@@ -31,4 +31,12 @@ End Function
 </script>
 
 <script lang="unknown">
-</script>
+</script>
+
+<script type="speculationrules">
+  {
+   "prerender": [
+  {"source": "list", "urls": ["https://a.test/foo"]}
+  ]
+  }
+  </script>