[FIX] website: fix save animated snippet

Before this commit, when dropping custom snippet (or saved snippet)
containing an animation in the page, the animated element of the
snippet remained hidden.

task-2664876

closes odoo/odoo#78493

X-original-commit: 61d7744ca988641bd4d8a4006350ec197eece25a
Signed-off-by: Quentin Smetz (qsm) <qsm@odoo.com>

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

@@ -2856,6 +2856,12 @@ options.registry.WebsiteAnimate = options.Class.extend({
         this.isAnimatedText = this.$target.hasClass('o_animated_text');
         this.$optionsSection = this.$overlay.data('$optionsSection');
     },
+    /**
+     * @override
+     */
+    async onBuilt() {
+        this.$target[0].classList.toggle('o_animate_preview', this.$target[0].classList.contains('o_animate'));
+    },
     /**
      * @override
      */