ssb: Before destroying a connection, show a message on why it is going away in the UI.

apps/ssb/tf-tab-connections.js

@@ -175,6 +175,9 @@ class TfTabConnectionsElement extends LitElement {
 					.map((x) => html`<li>${this.render_connection(x)}</li>`)}
 				${this.render_room_peers(connection.id)}
 			</ul>
+			<div ?hidden=${!connection.destroy_reason} class="w3-panel w3-red">
+				<p>${connection.destroy_reason}</p>
+			</div>
 		`;
 	}