propsPlugin
Register a prop (or a prop namespace) that can be used on any element. The handler runs whenever an element has that prop set; this is how use:bind, use:clickoutside and friends work — and how you add your own. See Directory for the built-in list.
# Signatures
- propsPlugin('use:tooltip', fn) matches a single prop name exactly.
- propsPluginNS('use', fn) claims the whole use:* namespace — the handler receives the part after the colon as localName.
- onMicrotask defaults to true so the handler runs on a microtask, after siblings are set and children exist. Pass false if you need the handler to fire synchronously while the element is being built.