fix: no-skip-heading-levels: h4 tag was not being validated (#442)

* Initial plan

* Fix no-skip-heading-levels rule missing h4 tag in validation array

Co-authored-by: yeonjuan <[email protected]>

---------

Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: yeonjuan <[email protected]>

Author: Copilot

packages/eslint-plugin/lib/rules/no-skip-heading-levels.js

@@ -40,7 +40,7 @@ module.exports = {
 
     return {
       Tag(node) {
-        if (!["h1", "h2", "h3", "h5", "h6"].includes(node.name)) {
+        if (!["h1", "h2", "h3", "h4", "h5", "h6"].includes(node.name)) {
           return;
         }
         headings.push({

packages/eslint-plugin/tests/rules/no-skip-heading-levels.test.js

@@ -45,6 +45,18 @@ ruleTester.run("no-skip-heading-levels", rule, {
 <h1>one heading</h1>
 </body>
 </html>
+`,
+    },
+    {
+      code: `
+<div>
+  <h1>Heading 1</h1>
+  <h2>Heading 2</h2>
+  <h3>Heading 3</h3>
+  <h4>Heading 4</h4>
+  <h5>Heading 5</h5>
+  <h6>Heading 6</h6>
+</div>
 `,
     },
   ],