Update request.ts wasm_response_send signature (#2122)

Update wasm_response_send function signature to match api by returning
bool instead of void (was causing assemblyscript example to break)

assembly-script/wamr_app_lib/request.ts

@@ -7,7 +7,7 @@ import * as console from './console'
 import * as timer from './timer'
 
 @external("env", "wasm_response_send")
-declare function wasm_response_send(buffer: ArrayBuffer, size: i32): void;
+declare function wasm_response_send(buffer: ArrayBuffer, size: i32): bool;
 
 @external("env", "wasm_register_resource")
 declare function wasm_register_resource(url: ArrayBuffer): void;
@@ -492,4 +492,4 @@ export function on_response(buffer_offset: i32, size: i32): void {
 
         trans.cb(resp);
     }
-}
+}