[IMP] website_blog : onboarding. The cover image of a blog post is editable (opacity, color, size, ...). Add a new tour, views improvements and new default images

addons/website/static/src/css/editor.css

@@ -85,7 +85,11 @@
 .editor_enable [data-oe-readonly]:hover {
   cursor: default;
 }
-
+/* Summernote not Support for placeholder text https://github.com/summernote/summernote/issues/581 */
+.o_editable[placeholder]:empty:not(:focus):before {
+    content: attr(placeholder);
+    opacity: 0.3;
+}
 /* Prevent the text contents of draggable elements from being selectable. */
 [draggable] {
   -moz-user-select: none;