base: Add examples to Bifunctor documentation
base: Add examples to Bifunctor documentation

shlevy/ghc,shlevy/ghc,sdiehl/ghc,ezyang/ghc,ezyang/ghc,ezyang/ghc,ezyang/ghc,shlevy/ghc,shlevy/ghc,shlevy/ghc,ezyang/ghc,sdiehl/ghc,shlevy/ghc,sdiehl/ghc,sdiehl/ghc,sdiehl/ghc,ezyang/ghc,ezyang/ghc,shlevy/ghc,sdiehl/ghc,sdiehl/ghc