add appservice ping client endpoint (MSC2659)

Signed-off-by: strawberry <strawberry@puppygock.gay>

src/api/router.rs

@@ -22,6 +22,7 @@ use crate::{client, server};
 pub fn build(router: Router<State>, server: &Server) -> Router<State> {
 	let config = &server.config;
 	let mut router = router
+        .ruma_route(client::appservice_ping)
 		.ruma_route(client::get_supported_versions_route)
 		.ruma_route(client::get_register_available_route)
 		.ruma_route(client::register_route)