On startup and on every change to the current URL - whether by changing tabs or by visiting a new page - the extension checks all link elements with a rel= property in the HTML for a value containing webmention. Based on the results, it sets the extension's icon appropriately.
This version adds a (manual) popup to show a page's h-card, if any. Under the covers, it also moves to the "Manifest v3" form, for better parity across browsers.
