Feature request: When opening assignment list in a browser, URL should also be outputted, similar to gh auth login, in case terminal is headless

E.g.:

```
$ gh classroom assignments --web
? Select a classroom: Introduction to Game Development
22 Assignments for Introduction to Game Development

Opening in your browser.
```

Versus:

```
$ gh auth login
? You're already logged into github.com. Do you want to re-authenticate? Yes
? What is your preferred protocol for Git operations? HTTPS
? How would you like to authenticate GitHub CLI? Login with a web browser

! First copy your one-time code: 306B-9B4C
Press Enter to open github.com in your browser...
! Failed opening a web browser at https://github.com/login/device
exec: "xdg-open,x-www-browser,www-browser,wslview": executable file not found in $PATH
Please try entering the URL in your browser manually
```