Planning to make 1.20 release in about one week

Hi! I looked over and replied to the remaining outstanding pull requests a couple of days ago. I'm happy to call what's in master now 1.20 (although I'm also happy if any of the outstanding pull requests make it in.) If nothing major happens I will make a release on the 15th. P.S. There are 360 commits since the last release according to `git log --pretty=oneline Cabal-v1.18.1.3..`. -- Johan