Inline edit message trigger

[rebeccaalpert]

Design here: patternfly/patternfly-design-kit#801

You can use the isEditable prop on Message to trigger the existing "edit" state seen in the videos Kayla has posted.

We likely only want to add the one response action (edit with pencil icon) below the message - need to add button, set up response actions, set up Message to accept response action, and update demos/tests so we can show similar behavior to what design is asking for.