Add X-Content-Type-Options header

For internet.nl tests. Please keep in mind that this only works on kubernetes deploys, _not_ on Github Pages.

pwa/docker/default.conf

@@ -12,6 +12,8 @@ server {
         root   /usr/share/nginx/html;
         index  index.html index.htm;
         try_files $uri $uri/ /index.html;
+
+        add_header X-Content-Type-Options nosniff;
     }
 
     #error_page  404              /404.html;