[FIX] web_editor: edition of monetary value

Issue: if the currency is before the value and we try to add a number at the begin of the value, the number is not saved (because the browser insert the number before the span).
Add a onEnableEditableArea in the rte to change the contenteditable value and the default behavior.

addons/web_editor/static/src/js/rte.js

@@ -546,9 +546,14 @@ var RTE = Widget.extend({
             if (dom.isImg($target[0])) {
                 $target.trigger('mousedown'); // for activate selection on picture
             }
+
+            rte.onEnableEditableArea($editable);
         }
     },
 
+    onEnableEditableArea: function ($editable) {
+    },
+
     onMouseup: function (event) {
         var $target = $(event.target);
         var $editable = $target.closest('.o_editable');

addons/web_editor/static/src/js/widgets.js

@@ -597,7 +597,13 @@ rte.Class.include({
     init: function (EditorBar) {
         this._super.apply(this, arguments);
         computeFonts();
-    }
+    },
+    onEnableEditableArea: function ($editable) {
+        if ($editable.data('oe-type') === "monetary") {
+            $editable.attr('contenteditable', false);
+            $editable.find('.oe_currency_value').attr('contenteditable', true);
+        }
+    },
 });
 
 /* list of font icons to load by editor. The icons are displayed in the media editor and