Small changes on the "Not Found" page

[tgxworld (Alan Tan)]

Fixed in

UX: "See more" on not found page should redirect to /top.

@youwiki

And also topic slug value for Google search input on this page is not actual for non-english sites.

@youwiki You’ll have to configure slug_generation_method to encoded if you want to have the full unicode support for slugs. Otherwise, it defaults to topic.