Tippy allows HTML strings to be passed as content but we do not use this
feature (we do pass HTML only as Element), so it's better to disable it
for increased security.
Ref: https://atomiks.github.io/tippyjs/v6/html-content/#string
Previous solution that re-purposed the 'hide' class by making it
`!important` had various unintended side-effects where jQuery .show() was
not able to outweight it. Use a separate class to prevent these
interactions.
By appending the tooltips to `document.body`, we can avoid any stacking context issues caused by surrounding element's CSS.
This uses [tippy.js](https://github.com/atomiks/tippyjs) instead of Fomantic popups. We should aim to replace all Fomantic popups with this eventually and then get rid of the Fomantic `popup` module completely.
