Design Component Library: Toasts/Snackbars/Alerts

[roraback]

Toasts in:

• Light Theme
• Dark Theme

For each Theme

• Default
• Danger?
• Success?

Should have optional icon on left and 'x' icon button on the right for manually dismissed toasts

[roraback]

Of note: a recent PR with changes (and screenshots) of how these currently look in the product: #22842

[zmb3]

This is tracked as a development task in #37260, so I assume there is no more design work to be done and this can be closed. Feel free to reopen if I am mistaken.