<!-- Code originally from <https://linkstyle.tiddlyspot.com/>, adapted by me to work just with icons -->
<!-- Notes:
- Anchor classes are selected via strict HTML attributes to avoid things like custom buttons from being stylized where they shouldn't; we will then need another rule to look for an explicit class to stylize other elements
- Currently this assumes that the icon field of a tiddler can only have an emoji, never an image URL