Add unreleased section to CHANGELOG post 0.48.0 release
Add unreleased section to CHANGELOG post 0.48.0 release

dipinhora/ponyc,ponylang/ponyc,ponylang/ponyc,dipinhora/ponyc,jemc/ponyc,ponylang/ponyc,jemc/ponyc,jemc/ponyc,dipinhora/ponyc