9.0.0

PRs:

className prop is gone. You must now pass classes using the classes object. This prop has been obsolete for a while.
Example of how to do it now:

          classes={{
            reactMde: "react-mde",
            suggestionsDropdown: "sug-dropdown",
          }}

textAreaProps prop is gone. You must now use the childProps. This prop has been obsolete for a while.
Example of how to do it now:

          childProps={{
            textArea: {
              a: 1
            }
          }}

For custom commands, the keyCommand field is gone. This was useless and was left there from the Draft.js times.

Commands can now have async execute functions. This is to facilitate adding the upload image functionality, since I am planning that to be a long running command, under the hoods.
Commands now can implement a handleKeyCommand handler. This function will be called for every keydown inside the textarea. If this function returns true, the command will be executed.
It is now possible use Cmd+B for bold, Cmd+I for italic and Cmd+k for link as shortcuts.