[[IndieWeb]] cross-site interactions.

### Validate a Receiver

<form method=post action=/webmention>
<label><small>Target URL:</small><br>
<input name=target></label><br>
<button>Inspect</button>
</form>

### Send a Webmention

<form method=post action=/webmention>
<label><small>Source URL:</small><br>
<input name=target></label><br>
<label><small>Target URL:</small><br>
<input name=target></label><br>
<button>Send</button>
</form>

### Scan and send all Webmentions

<form method=post action=/webmention/sender>
<label><small>Source URL:</small><br>
<input name=target></label><br>
<button>Send</button>
</form>