first working version with event reception in kanban

frontend/src/urls.svelte.js

@@ -15,6 +15,12 @@ export function drop(url){
     });
 }
 
+export function eventStream(updateHandler){
+	const es = new EventSource(api('bus'), {withCredentials: true});
+	if (updateHandler) es.addEventListener('UPDATE', updateHandler);
+	return es;
+}
+
 export function patch(url,data){
     return fetch(url,{
         credentials : 'include',