Add link-to-search on "Package not found" page

[lspitzner]

i have a shortcut in browser to navigate to specific package. when i make error typing/remembering name, it would be nice if i'd get a link to search for this package. I.e.

https://hackage.haskell.org/packages/foo
->
https://hackage.haskell.org/packages/search?terms=foo

(Similar to wikipedia's second link, see https://en.wikipedia.org/wiki/Haksell)

[dcoutts]

The approach here would be to use a different error page template and then make that template provide a link to the search, with the term filled out.

[gbaz]

@sooryan this looks like another ticket that may relate to your work?

[gbaz]

Should be fixed by merge of #551