Library haddocks should have hyperlinked sources

Haddock's hyperlinked sources are very useful for navigating library implementations. It would be nice if the haddocks accompanying the GHC releases and the master haddocks could include them.

Compare

https://downloads.haskell.org/ghc/latest/docs/html/libraries/base-4.15.0.0/src/Control-Applicative.html

and

https://ghc.gitlab.haskell.org/ghc/doc/libraries/base-4.16.0.0/src/Control-Applicative.html

against

http://hackage.haskell.org/package/base-4.14.1.0/docs/src/Control.Applicative.html