CodeEditor - add example showcasing custom keyboard shortcuts

[thatblindgeye]

Is this a new component or an extension of an existing one?
CodeEditor

Describe the feature
Followup to an update made to the a11y docs in org: patternfly/patternfly-org#3799 (comment)

Content showing how to add custom keyboard shortcuts are removed in that PR, but we don't really document elsewhere how to do so.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs.

[github-actions]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs.

[github-actions]

This issue has been automatically marked as stale because it has not had recent activity.