Accessibility updates - main landmark roles (#17106)

* Removed multiple main tags from home page

Signed-off-by: chaitanyakaranam <chaitanya.karanam@yahoo.com>

* Removed multiple occurances of main in case-studies page

Signed-off-by: chaitanyakaranam <chaitanya.karanam@yahoo.com>

* Replaced css for main tag with .main-section class

Signed-off-by: ChaitanyaKaranam <karanam.krishna.25@gmail.com>

* Added main landmark role for all the pages

Signed-off-by: ChaitanyaKaranam <karanam.krishna.25@gmail.com>

* Force checks.

request-checks: true

layouts/_default/baseof.html

@@ -8,20 +8,22 @@
 		{{ block "hero" . }}
 		<!--  HERO  -->
 		<section id="hero" class="light-text">
-			<main>
+			<div class="main-section">
 				<div id="headlineWrapper">
 					<h1>{{ block "hero-title" . }}{{ .Params.bigheader | default .Title }}{{ end }}</h1>
 					<h5>{{ .Params.abstract }}</h5>
 				</div>
 				{{ block "hero-more" . }}{{ end }}
-			</main>
+			</div>
 		</section>
 		{{ block "post-hero" . }}{{ end }}
 		{{ end }}
-    
-    <article class="page-content">
-      {{ block "main" . }}{{ end }}
-    </article>
+	
+	<main>
+		<article class="page-content">
+		  {{ block "main" . }}{{ end }}
+		</article>
+	</main>
 
 		{{ partialCached "footer.html" . }}
 		{{ partialCached "footer-scripts.html" . }}