message: add some button feedback
diff: @@ -100,7 +100,9 @@ const char HTTP_STYLE[] PROGMEM = "<style>"
  "dt{font-weight:bold}dd{margin:0;padding:0 0 0.5em 0;min-height:12px}"
  "td{vertical-align: top;}"
  ".h{display:none}"
  +"button{transition: 0s opacity;transition-delay: 3s;transition-duration: 0s;cursor: pointer}"
  "button.D{background-color:#dc3630}"
  +"button:active{opacity:50% !important;cursor:wait;transition-delay: 0s}"
  // invert
  "body.invert,body.invert a,body.invert h1 {background-color:#060606;color:#fff;}"
  "body.invert .msg{color:#fff;background-color:#282828;border-top:1px solid #555;border-right:1px solid #555;border-bottom:1px solid #555;}"
  