Add `changelog` to extra-source-files
Add `changelog` to extra-source-files

So that it'll show up on Hackage
edsko/cabal,thomie/cabal,sopvop/cabal,rimmington/cabal,mmakowski/cabal,thoughtpolice/cabal,rimmington/cabal,fugyk/cabal,eric-stanley/cabal,eric-stanley/cabal,typelead/epm,corngood/cabal,thoughtpolice/cabal,lukexi/cabal,sopvop/cabal,Peaker/cabal,plow-technologies/cabal,corngood/cabal,beni55/cabal,kosmikus/cabal,Heather/cabal,Helkafen/cabal,garetxe/cabal,gridaphobe/cabal,enolan/cabal,kolmodin/cabal,themoritz/cabal,headprogrammingczar/cabal,beni55/cabal,valderman/cabal,typelead/epm,trskop/cabal,ghc-android/cabal,triplepointfive/cabal,ian-ross/cabal,lukexi/cabal,trskop/cabal,gridaphobe/cabal,triplepointfive/cabal,Helkafen/cabal,mydaum/cabal,martinvlk/cabal,thomie/cabal,Peaker/cabal,christiaanb/cabal,sopvop/cabal,headprogrammingczar/cabal,edsko/cabal,anton-dessiatov/cabal,themoritz/cabal,ian-ross/cabal,martinvlk/cabal,kolmodin/cabal,fugyk/cabal,gbaz/cabal,seereason/cabal,kosmikus/cabal,ghc-android/cabal,bennofs/cabal,gbaz/cabal,seereason/cabal,plumlife/cabal,mmakowski/cabal,plow-technologies/cabal,valderman/cabal,x-y-z/cabal,enolan/cabal,mydaum/cabal,anton-dessiatov/cabal,themoritz/cabal,x-y-z/cabal,mightybyte/cabal,randen/cabal,bennofs/cabal,randen/cabal,plumlife/cabal,christiaanb/cabal,Heather/cabal,mightybyte/cabal,garetxe/cabal