Add a fixed button for go to top on website without it.

Go to top

// ==UserScript==
// @name        go to top
// @namespace   gototop
// @description Add a button to go to top
// @include     *
// @version     1
// @grant       none
// @require     https://cdnjs.cloudflare.com/ajax/libs/zepto/1.1.6/zepto.min.js
// ==/UserScript==
$(document).ready(function () {
  $('body').append('<div id=\'gototop\'>&#8593;</div>');
  $('#gototop').css({
    'position': 'fixed',
    'left': '96.5%',
    'bottom': '5px',
    'padding': '5px',
    'width': '50px',
    'z-index': '99999',
    'font-size': '26px',
    'text-align': 'center',
    'vertical-align': 'middle',
    'background': 'rgba(0,0,0,0.8)',
    'color': '#efefef',
    'border-radius': '10px',
    'box-shadow': 'inset 0 0 10px 10px rgba(0,0,0,0.5)',
    "cursor": "pointer"
  });
  $('#gototop').on('mousedown', function (e) {
    switch(e.which) {
      case 1:
        document.body.scrollTop = document.documentElement.scrollTop = 0;
        break;
      case 3:
        $('#gototop').remove();
        break;
      case 2:
      default:
        document.body.scrollTop = document.documentElement.scrollTop = 0;
        break;
    }
    
  });
});

Right click will remove it.