[FIX] web_editor: open customize menus to the left/right

Open customize options menus to the left if there is not enough space on
the right.

addons/web_editor/static/src/js/editor/snippets.options.js

@@ -298,8 +298,16 @@ var SnippetOption = Widget.extend({
      * @param {Event} ev
      */
     _onLinkEnter: function (ev) {
-        var $li = $(ev.currentTarget).parent(':hasData');
-        if (!$li.length) {
+        var $li = $(ev.currentTarget).parent();
+        if ($li.is('.dropdown-submenu')) {
+            var $menu = $li.children('.dropdown-menu');
+            if ($menu.length) {
+                var menuRightPosition = $li.offset().left + $li.outerWidth() + $menu.outerWidth();
+                $menu.toggleClass('o_open_to_left', menuRightPosition > $(window).outerWidth());
+            }
+        }
+
+        if (!$li.is(':hasData')) {
             return;
         }
         this.__click = false;

addons/web_editor/static/src/less/web_editor.ui.less

@@ -452,6 +452,11 @@ html[lang] > body.editor_enable [data-oe-translation-state] {
                                     display: block;
                                     left: 100%;
                                     top: 0;
+
+                                    &.o_open_to_left {
+                                        left: auto;
+                                        right: 100%;
+                                    }
                                 }
                             }
                             &.dropdown-submenu:before {