[blog] Lint duplicate h1 on the page

[oliviertassinari]

This new lint fails the ci when it sees a h1 or duplicated h1 in a page where h1 isn't the first element #40784 (comment).

For example:

diff --git a/docs/data/material/components/alert/alert.md b/docs/data/material/components/alert/alert.md
index 1f1a903f2c..bcde949fe0 100644
--- a/docs/data/material/components/alert/alert.md
+++ b/docs/data/material/components/alert/alert.md
@@ -6,13 +6,15 @@ githubLabel: 'component: alert'
 waiAria: https://www.w3.org/WAI/ARIA/apg/patterns/alert/
 ---

+a
+
 # Alert

 <p class="description">Alerts display brief messages for the user without interrupting their use of the app.</p>

 {{"component": "modules/components/ComponentLinkHeader.js"}}

-## Introduction
+# Introduction

 Alerts give users brief and potentially time-sensitive information in an unobtrusive manner.

diff --git a/docs/pages/blog/2022-tenerife-retreat.md b/docs/pages/blog/2022-tenerife-retreat.md
index 0d0827075e..694c7fea6f 100644
--- a/docs/pages/blog/2022-tenerife-retreat.md
+++ b/docs/pages/blog/2022-tenerife-retreat.md
@@ -7,6 +7,8 @@ tags: ['Company']
 card: true
 ---

+# A
+
 One of the toughest challenges to overcome as a fully remote team is fostering a supportive and inclusive company culture.
 How do you build trust, comradery, and—dare I say it?—_friendships_, when there are so few opportunities for spontaneous social interactions in our daily work routines?

[mui-bot]

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[noraleonte]

LGTM 🎉