Update shortcuts to reflect Component Browser design docs.

[farmaazon]

Pull Request Description

When no node is edited, Enter creates a new one (opening Component Browser). The shortcut for entering node was changed to cmd + Enter

Checklist

Please include the following checklist in your PR:

• The documentation has been updated if necessary.
• All code conforms to the
  Scala,
  Java,
  and
  Rust
  style guides.
• All code has been tested:
  • Unit tests have been written where possible.
  • If GUI codebase was changed: Enso GUI was tested when built using BOTH
    ./run ide build and ./run ide watch.