add "scroll to top" button to timelines and notifications

src/components/timeline/timeline.js

@@ -29,6 +29,7 @@ const Timeline = {
   ],
   data () {
     return {
+      showScrollTop: false,
       paused: false,
       unfocused: false,
       bottomedOut: false,
@@ -123,6 +124,9 @@ const Timeline = {
     this.$store.commit('setLoading', { timeline: this.timelineName, value: false })
   },
   methods: {
+    scrollToTop () {
+      window.scrollTo({ top: this.$el.offsetTop })
+    },
     stopBlockingClicks: debounce(function () {
       this.blockingClicks = false
     }, 1000),
@@ -222,6 +226,7 @@ const Timeline = {
       }
     },
     handleScroll: throttle(function (e) {
+      this.showScrollTop = this.$el.offsetTop < window.scrollY
       this.determineVisibleStatuses()
       this.scrollLoad(e)
     }, 200),

src/components/timeline/timeline.vue

@@ -2,6 +2,14 @@
   <div :class="['Timeline', classes.root]">
     <div :class="classes.header">
       <TimelineMenu v-if="!embedded" />
+      <button
+        v-if="showScrollTop"
+        class="button-unstyled scroll-to-top-button"
+        type="button"
+        @click="scrollToTop"
+      >
+        <FAIcon icon="circle-up" />
+      </button>
       <button
         v-if="showLoadButton"
         class="button-default loadmore-button"