Further notification improvements

[fregante]

To do

• Restore warning style after:
  • More default toast types (toast.info(), toast.warn()) timolins/react-hot-toast#29
• Set close button’s opacity to 0 until the user hovers the notification, to make it look cleaner
• Show close button by default or not? In my previous PR I mistakenly defaulted it to always showing it:
  • Notification improvements (timer, dismissal) #2214
    ❌ Maybe not, because I think it makes sense that notifications can be closed
• Maybe replace initToaster with proper React component as part of the main <App/> (it currently calls its own React.render())
  ❌ Maybe not, because notify also/especially works in the content script, which doesn't necessarily have a single React root.

Done

• Automatically append the original error:

- notify.error({error, message: `Stuff happened: ${getErrorMessage(error)}`})
+ notify.error({error, message: "Stuff happened", decorate: true})

• Move the notifications slightly to the left when the sidebar is open
• Bricks seem to use Notify.js’ options directly, we should replace them with a simple {duration, type} object:
  • Replace content script notifications #2102 (comment)
• Improve Close button position/sizing

[fregante]

• Will just wait for More default toast types (toast.info(), toast.warn()) timolins/react-hot-toast#29