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/case-studies/list.html

@@ -10,7 +10,7 @@
 {{ end }}  
 {{ $featured := (where $pages "Params.featured" true).ByWeight | first 4 }}
 <section id="mainContent">
-	<main>
+	<div class="main-section">
 		<div class="content">
 			<div class="case-studies">
 				{{ range $featured }}
@@ -18,13 +18,13 @@
 				{{ end }}
 			</div>
 		</div>
-	</main>
+	</div>
 </section>
 {{ $featuredVideos := where .Pages ".Params.video" "!=" nil }}
 {{ with $featuredVideos }}
 {{ with index $featuredVideos 0 }}
 <section id="video">
-	<main>
+	<div class="main-section">
 		<div>
 			<h4><i>"{{ .Params.quote | html }}"</i></h4>
 			{{ $img := .Resources.GetMatch "video.png" }}
@@ -32,7 +32,7 @@
 			{{ with $small }}<img src="{{ .RelPermalink }}" alt="{{ .Title }}">{{ end }}
 		</div>
 		<div style= "padding-left: 40px;"><button onclick="kub.showVideo()">{{ with $img }}<img src="{{ .RelPermalink }}" alt="Box video">{{ end }}<h6>Kubernetes at Box</h6></button></div>
-	</main>
+	</div>
 	<div id="videoPlayer">
 		<iframe data-url="{{ .Params.video | safeURL }}" frameborder="0" allowfullscreen="true"></iframe>
 		<button id="closeButton"></button>
@@ -41,7 +41,7 @@
 {{ end }}
 {{ end }}
 <section id="users">
-	<main>
+	<div class="main-section">
 		<h3>{{ .Title }}</h3>
 		<div id="usersGrid">
 			{{ range $pages.ByTitle }}
@@ -60,7 +60,7 @@
 			{{ end }}
 			<a target="_blank" href="https://docs.google.com/a/google.com/forms/d/e/1FAIpQLScuI7Ye3VQHQTwBASrgkjQDSS5TP0g3AXfFhwSM9YpHgxRKFA/viewform" class="tell-your-story"><img src="/images/case_studies/story.png" alt="{{ T "layouts_case_studies_list_tell" }}"></a>
 		</div>
-	</main>
+	</div>
 </section>
 {{ .Content }}
 {{ end }}