New design for the default 404 page

[skttl]

Prerequisites

• I have added steps to test this contribution in the description below

If there's an existing issue for this PR then this fixes #9562

Description

This one adds a new view for the 404 page

When not in debug mode, it will only write "Page Not Found", like so:

Testing

Navigate to a non existing url, and verify that you no longer get the old, ugly 404 page.

[umbrabot]

Hi there @skttl, thank you for this contribution! 👍

While we wait for one of the Core Collaborators team to have a look at your work, we wanted to let you know about that we have a checklist for some of the things we will consider during review:

• It's clear what problem this is solving, there's a connected issue or a description of what the changes do and how to test them
• The automated tests all pass (see "Checks" tab on this PR)
• The level of security for this contribution is the same or improved
• The level of performance for this contribution is the same or improved
• Avoids creating breaking changes; note that behavioral changes might also be perceived as breaking
• If this is a new feature, Umbraco HQ provided guidance on the implementation beforehand
• The contribution looks original and the contributor is presumably allowed to share it

Don't worry if you got something wrong. We like to think of a pull request as the start of a conversation, we're happy to provide guidance on improving your contribution.

If you realize that you might want to make some changes then you can do that by adding new commits to the branch you created for this work and pushing new commits. They should then automatically show up as updates to this pull request.

Thanks, from your friendly Umbraco GitHub bot 🤖 🙂

[bjarnef]

The no-js should probably not be applied unless you have some javascript to remove the script.

Alternatively add something like this:

<script>
document.documentElement.classList.remove("no-js");
</script>

[skttl]

Should probably be removed from https://github.com/umbraco/Umbraco-CMS/blob/v9/contrib/src/Umbraco.Web.UI/umbraco/UmbracoWebsite/NoNodes.cshtml too :)

[mikecp]

Hi @skttl ,

Thanks for this PR 👍 , it makes the 404 look better yet still calling to be customized 😉