Update changelog.md to include all changes from v0.31.0 to v0.32.0
Update changelog.md to include all changes from v0.31.0 to v0.32.0

Reviewed By: colriot

Differential Revision: D18477543

fbshipit-source-id: bafb52a38bdcf7ec92a9205a4b8535b0539d4e72

facebook/litho,facebook/litho,facebook/litho,facebook/litho,facebook/litho,facebook/litho