Notifications: use heiristic to add the notification inline

[humitos]

We should be able to DocumentationTool class to detect what's the HTML generator and use specific CSS selectors to inject the notification in the document with inline-block position so it doesn't cover any content.

[agjohnson]

The work around a central UI for flyout/notifications etc would supersede this work so we'll come back to this if it is something we want.

[humitos]

Yes. I "created an issue to create issues" for the required work. I'm linking it here, so we have all of these issues backlinked somewhere.

• Create issues for new addons UI #569

I'm closing this one for now since it doesn't make too much sense to move forward with this approach without further discussion and experiment with the new UI.