get rid of older messages when scrolling down in chat to keep it from bloating dom

src/components/chat/chat.js

@@ -241,6 +241,7 @@ const Chat = {
         this.fetchChat({ maxId: this.currentChatMessageService.minId })
       } else if (this.bottomedOut(JUMP_TO_BOTTOM_BUTTON_VISIBILITY_OFFSET)) {
         this.jumpToBottomButtonVisible = false
+        this.$store.dispatch('cullOlderMessages', this.currentChatMessageService.chatId)
         if (this.newMessageCount > 0) {
           // Use a delay before marking as read to prevent situation where new messages
           // arrive just as you're leaving the view and messages that you didn't actually