Accessibility Updates (#16633)

* Fixed accessibility issues in home page

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

* Fixed accessibility issues for docs/home page

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

* Fixed accessibility issues for /partners page

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

* Fixed accessibility issues for /community page

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

* Update layouts/partials/header.html

Co-Authored-By: Tim Bannister <tim@scalefactory.com>

* Update layouts/partials/footer-scripts.html

Co-Authored-By: Tim Bannister <tim@scalefactory.com>

* Update layouts/index.html

Co-Authored-By: Tim Bannister <tim@scalefactory.com>

* Update content/en/partners/_index.html

Co-Authored-By: Tim Bannister <tim@scalefactory.com>

* Update content/en/community/_index.html

Co-Authored-By: Tim Bannister <tim@scalefactory.com>

* Added missing quotes

* Added landmark roles for search bar and footer

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

* Changed images alt text

Changed alt text from 'kubernetes community' to 'Kubernetes Conference Gallery'

* Removed verb from iframe title

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

* Change alt text for GitHub image

Co-Authored-By: Tim Bannister <tim@scalefactory.com>

* Few alt text changes

* Modified alt text

layouts/docs/docsportal_home.html

@@ -43,7 +43,7 @@
         {{ end }}
       </ul>
       <br><br>
-      <button id="btn-concepts" class="button" onClick="location.href='{{ .button_path | relLangURL }}';">{{ .button }}</button>
+      <button id="btn-concepts" class="button" onClick="location.href='{{ .button_path | relLangURL }}';" aria-label="{{ .title }}">{{ .button }}</button>
     </div>
   {{ end }}
 {{ end }}