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/partials/header.html

@@ -1,7 +1,7 @@
 <div id="cellophane" onclick="kub.toggleMenu()"></div>
 
 <header>
-    <a href="{{ site.Home.RelPermalink }}" class="logo"></a>
+    <a href="{{ site.Home.RelPermalink }}" class="logo" title="Production-Grade Container Orchestration - Kubernetes" aria-label="Kubernetes website"></a>
 
     <div class="nav-buttons" data-auto-burger="primary">
         <ul class="global-nav">