Implement Warning tool redesign

[TatianaFomina]

Update warning tool appearance according to the mockups. For precise figma mockups contact @TatianaFomina or @neSpecc

New design examples:

Empty

Filled

[collimarco]

Maybe this "warning" block could be a more generic block (e.g. alert, callout).

e.g. https://getbootstrap.com/docs/5.3/components/alerts/

The only changes needed would be:

1. Make title optional
2. Add a way for the user to select the alert type (primary, secondary, warning, danger, etc.)

[collimarco]

My suggestion above would also make Editor.js more aligned with current practices, like GitHub markdown:

https://github.com/orgs/community/discussions/16925

[neSpecc]

@collimarco good idea. Would you be able to implement it?