Fix accessibility issues

Also, remove duplicate img

www/components/CaseStudies/benchmark.tsx

@@ -10,10 +10,12 @@ const Benchmark = () => {
           <img
             className="mb-10 w-full lg:w-auto lg:mb-0 lg:h-44 lg:mr-14 hidden lg:block"
             src={`${basePath}/images/benchmark.svg`}
+            alt="Benchmark illustration"
           />
           <img
             className="mb-10 w-full lg:w-auto lg:mb-0 lg:h-44 lg:mr-14 lg:hidden"
             src={`${basePath}/images/benchmark--mobile.svg`}
+            alt="Benchmark illustration"
           />
           <div className="px-12 py-5 lg:px-0 lg:py-0">
             <p className="text-xl text-white">Built for speed and reliability</p>
@@ -21,7 +23,9 @@ const Benchmark = () => {
               <span className="block">
                 Supabase outperforms equivalent systems by more than 300%.
               </span>
-              <span className="block">Sign up for our public benchmark release and we'll send it to your inbox.</span>
+              <span className="block">
+                Sign up for our public benchmark release and we'll send it to your inbox.
+              </span>
             </p>
           </div>
         </div>

www/components/Hero.tsx

@@ -88,6 +88,7 @@ const Hero = () => {
                         style={{ padding: '56.25% 0 0 0' }}
                       >
                         <iframe
+                          title="Demo video showcasing Supabase"
                           className="absolute w-full h-full rounded-b-md"
                           src="https://www.youtube-nocookie.com/embed/dBOSUER_5T4?playlist=dBOSUER_5T4&autoplay=1&loop=1&controls=0&modestbranding=1&rel=0&disablekb=1&mute=1&muted=1"
                           style={{ top: 0, left: 0 }}
@@ -95,7 +96,7 @@ const Hero = () => {
                           allow="autoplay; modestbranding; encrypted-media"
                         />
                       </div>
-                      {/* 
+                      {/*
                       Replace src with the following if have preference:
                       Vimeo:   https://player.vimeo.com/video/485959063?loop=1&autoplay=1
                       Youtube: https://www.youtube-nocookie.com/embed/dBOSUER_5T4?playlist=dBOSUER_5T4&autoplay=1&loop=1&controls=0&modestbranding=1&rel=0&disablekb=1&mute=1&muted=1

www/components/Nav/index.tsx

@@ -189,16 +189,7 @@ const Nav = (props: Props) => {
           <div className="flex items-center">
             <div className="flex-shrink-0 flex items-center">
               <img
-                className="block lg:hidden h-6 w-auto"
-                src={
-                  darkMode
-                    ? `${basePath}/images/logo-dark.png`
-                    : `${basePath}/images/logo-light.png`
-                }
-                alt="Logo"
-              />
-              <img
-                className="hidden lg:block h-6 w-auto"
+                className="block h-6 w-auto"
                 src={
                   darkMode
                     ? `${basePath}/images/logo-dark.png`