fix: expose loading.throttle as an option (#3953)

lib/app/components/nuxt-loading.vue

@@ -17,7 +17,7 @@ export default {
       percent: 0,
       show: false,
       canSuccess: true,
-      throttle: 200,
+      throttle: <%= loading.throttle %>,
       duration: <%= loading.duration %>,
       height: '<%= loading.height %>',
       color: '<%= loading.color %>',

lib/common/nuxt.config.js

@@ -175,6 +175,7 @@ export default {
     color: 'black',
     failedColor: 'red',
     height: '2px',
+    throttle: 200,
     duration: 5000,
     rtl: false
   },