[IMP] pad: add mobile support for pad widget

In mobile devices, the pad widget did not behave in a satisfactory
manner.  Also, once it was in fullscreen mode, it was not possible to
come back to normal mode.

Task: #31545
PR: #15817

addons/pad/static/src/css/etherpad.css

@@ -21,6 +21,16 @@
     font-size: 14px;
 }
 
+@media (max-width: 767px) {
+    .oe_pad_switch {
+        left: auto;
+        right: 5px;
+    }
+    html .o_scroll_hidden {
+        overflow: hidden;
+    }
+}
+
 .oe_pad_switch:hover{
     background-image: -webkit-linear-gradient(top, #f4f4f4, #e4e4e4);
 }

addons/pad/static/src/js/pad.js

@@ -178,6 +178,7 @@ var FieldPad = AbstractField.extend({
     _onToggleFullScreen: function () {
         this.$el.toggleClass('oe_pad_fullscreen mb0');
         this.$('.oe_pad_switch').toggleClass('fa-expand fa-compress');
+        this.$el.parents('.o_touch_device').toggleClass('o_scroll_hidden');
     },
 });