docs: use gif from github for social image instead of static img

Author: lukecotter

lana-docs-site/docusaurus.config.ts

@@ -66,7 +66,7 @@ const config: Config = {
       isCloseable: true,
     },
     // Replace with your project's social card
-    image: 'img/lana-timeline.png',
+    image: `https://raw.githubusercontent.com/${organizationName}/${projectName}/main/lana/assets/v1.18/lana-preview.gif`,
     metadata: [
       {
         name: 'keywords',