Improve the formatting of `Page Not Found` page

[JordanJordanov]

What would you like to be added: We need to advertise the suggestions (if we have such) in the error page.

• The Page Not Found tile should be smaller font-size
• The focus should be on the suggestion (whatever this measn, e.g. bold, bigger font)

Why is this needed: People hitting a moved page do not recognize easily that they have suggestions for where the page might be moved.

[Kostov6]

I will hand over this issue to @n-boshnakov and provide support if needed

[Kostov6]

Files of interest are 404.sh and 404.html