[IMP] qweb, blockdom, components: t-on with modifiers

supported modifiers: capture, prevent, stop, self.

src/blockdom/config.ts

@@ -16,12 +16,13 @@ export const config = {
   // this is the main event handler. Every event handler registered with blockdom
   // will go through this function, giving it the data registered in the block
   // and the event
-  mainEventHandler: (data: any, ev: Event) => {
+  mainEventHandler: (data: any, ev: Event, currentTarget?: EventTarget | null): boolean => {
     if (typeof data === "function") {
       data(ev);
     } else if (Array.isArray(data)) {
       data = filterOutModifiersFromData(data).data;
       data[0](data[1], ev);
     }
+    return false;
   },
 };