Add information about ToastRack styling to the toast widget documentation

[mxovd]

There's no mention of the ToastRack widget in the Toast widget documentation. It could be useful to mention that styling the ToastRack is necessary to move the position of notifications. Maybe something like this:

If you wish to change the location of Toasts, it is possible by targeting the ToastRack CSS type. For example:

ToastRack {
        align: right top;
    }

I can make a PR if it is acceptable.

[github-actions]

We found the following entry in the FAQ which you may find helpful:

• How do I center a widget in a screen?

Feel free to close this issue if you found an answer in the FAQ. Otherwise, please give us a little time to review.

This is an automated reply, generated by FAQtory

[willmcgugan]

PR would be appreciated!