[BUG] User can still changes the content when readOnly is true with kb style shortcuts

[dennisat]

Your environment

Mac: 13.5.1 Chrome: 116.0.5845.140

Repro

1. Do: As a developer, set the readOnly property to true
2. Do: As a user, select a word from the markdown text and press ctrl-b (to make it bold)
3. Observerd: The word got in bold!
4. Expected: No change should done on readOnly={true}