Apply suggestions from code review

Co-authored-by: Karina Kwiatek <6197148+raccube@users.noreply.github.com>
Co-authored-by: Georg Gadinger <nilsding@nilsding.org>

public/404.html

@@ -4,6 +4,7 @@
   <meta charset="utf-8">
   <title>Page not found</title>
   <meta name="viewport" content="width=device-width,initial-scale=1">
+  <meta name="theme-color" content="#f0edf4">
   <style>
     :root {
       --primary: #5e35b1;
@@ -121,7 +122,7 @@
           srcset="/images/errors/small/404.png 576w,
                   /images/errors/medium/404.png 768w,
                   /images/errors/original/404.png 1200w">
-        <img src="/images/errors/small/404.png"/>
+        <img src="/images/errors/small/404.png" alt="A raccoon peeking out of a bin, looking confused" />
       </picture>
     </div>
     <div class="error-text-container">

public/422.html

@@ -121,7 +121,7 @@
           srcset="/images/errors/small/404.png 576w,
                   /images/errors/medium/404.png 768w,
                   /images/errors/original/404.png 1200w">
-        <img src="/images/errors/small/404.png"/>
+        <img src="/images/errors/small/404.png" alt="A raccoon peeking out of a bin, looking confused" />
       </picture>
     </div>
     <div class="error-text-container">

public/500.html

@@ -121,7 +121,7 @@
           srcset="/images/errors/small/500.png 576w,
                   /images/errors/medium/500.png 768w,
                   /images/errors/original/500.png 1200w">
-        <img src="/images/errors/small/500.png"/>
+        <img src="/images/errors/small/500.png" alt="A raccoon smashing a server with a hammer" />
       </picture>
     </div>
     <div class="error-text-container">