Apply suggestions from code review

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

public/422.html

@@ -4,6 +4,7 @@
   <meta charset="utf-8">
   <title>Whoops?</title>
   <meta name="viewport" content="width=device-width,initial-scale=1">
+  <meta name="theme-color" content="#f0edf4">
   <style>
     :root {
       --primary: #5e35b1;

public/500.html

@@ -4,6 +4,7 @@
   <meta charset="utf-8">
   <title>Internal Server Error</title>
   <meta name="viewport" content="width=device-width,initial-scale=1">
+  <meta name="theme-color" content="#f0edf4">
   <style>
     :root {
       --primary: #5e35b1;