xhr: implement async http client

src/apiweb.zig

@@ -5,6 +5,7 @@ const Console = @import("jsruntime").Console;
 const DOM = @import("dom/dom.zig");
 const HTML = @import("html/html.zig");
 const Events = @import("events/event.zig");
+const XHR = @import("xhr/xhr.zig");
 
 pub const HTMLDocument = @import("html/document.zig").HTMLDocument;
 
@@ -14,4 +15,5 @@ pub const Interfaces = generate.Tuple(.{
     DOM.Interfaces,
     Events.Interfaces,
     HTML.Interfaces,
+    XHR.Interfaces,
 });