fix(vuepress-plugin-back-to-top): fit the vuepress-plugin-smooth-scroll

packages/@vuepress-reco/vuepress-plugin-back-to-top/bin/BackToTop.vue

@@ -12,8 +12,6 @@ export default {
   data () {
     return {
       visible: false,
-      interval: null,
-      isMoving: false,
       /* eslint-disable no-undef */
       customStyle: CUSTOM_STYLE,
       visibilityHeight: VISIBILITY_HEIGHT
@@ -24,34 +22,13 @@ export default {
   },
   beforeDestroy () {
     window.removeEventListener('scroll', this.handleScroll)
-    if (this.interval) {
-      clearInterval(this.interval)
-    }
   },
   methods: {
     handleScroll () {
       this.visible = window.pageYOffset > this.visibilityHeight
     },
     backToTop () {
-      if (this.isMoving) return
-      const start = window.pageYOffset
-      let i = 0
-      this.isMoving = true
-      this.interval = setInterval(() => {
-        const next = Math.floor(this.easeInOutQuad(10 * i, start, -start, 500))
-        if (next <= 0) {
-          window.scrollTo(0, 0)
-          clearInterval(this.interval)
-          this.isMoving = false
-        } else {
-          window.scrollTo(0, next)
-        }
-        i++
-      }, 16.7)
-    },
-    easeInOutQuad (t, b, c, d) {
-      if ((t /= d / 2) < 1) return c / 2 * t * t + b
-      return -c / 2 * (--t * (t - 2) - 1) + b
+      window.scrollTo(0, 0)
     }
   }
 }