Core htmx perf Tests

• history snapshot cleaning should be fast6ms ‣

  var size = 5 * 1024 // ~350K in size, about the size of CNN's body tag :p
  var workArea = getWorkArea()
  var html = "<div class='foo bar'>Yay, really large HTML documents are fun!</div>\n"
  html = stringRepeat(html, size)
  workArea.insertAdjacentHTML('beforeend', html)
  var start = performance.now()
  htmx._('cleanInnerHtmlForHistory')(workArea)
  var end = performance.now()
  var timeInMs = end - start
  chai.assert(timeInMs < 50, 'Should take less than 50ms on most platforms')