PreJoin component doesn't have ability to make user name input read only

### Describe the problem If you already have some user auth system, user name can be already known, and app may not expect it can be changed. ### Describe the proposed solution Maybe it worth just add related option to component props... ### Alternatives considered Right now I'm using following workaround in parent component: ``` useEffect(() => { const username = document.getElementById("username") as HTMLInputElement if(username) { username.disabled = true } }) ``` ### Importance nice to have