Add 'scroll past content' to the source viewer

[I3ck]

When following the link https://hackage.haskell.org/package/megaparsec-7.0.5/docs/src/Text.Megaparsec.State.html#PosState
one would expect to have PosState at the top of the page.
But since it's at the end of the content, the browser won't scroll to it and the user still has to search for it.
Consider e.g. adding a margin at the bottom of at least one page height.