message: Bump changelog after 2.0.0-alpha.9 release.
  Original commit:
diff: # Next Release
  +# Enso 2.0.0-alpha.9 (2021-07-16)
  +
  <br/>![New Features](/docs/assets/tags/new_features.svg)
  #### Visual Environment
  -- [Improved undo-reddo][1653]. Several new operations are now supported by
  - undo-redo:
  - - node selection;
  - - enabling and disabling a visualization;
  - - entering and leaving a node.
  +- [Improved undo-redo][1653]. Node selection, enabling/disabling visualisations
  + and entering a node are now affected by undo/redo and are restored on project
  + startup.
  <br/>
  