feat: Update shared-environments js doc to recommend v8 (#10931)

Author: AbhiPrasad

docs/platforms/javascript/common/best-practices/shared-environments.mdx

@@ -24,6 +24,12 @@ keywords:
   ]
 ---
 
+<Note>
+
+We recommend using JavaScript SDK `8.x` and above when using the SDK with shared environments. Check out our [migration docs](https://docs.sentry.io/platforms/javascript/migration/) to upgrade from an older SDK version to `8.x` and above.
+
+</Note>
+
 These best practices are relevant for you if you set up Sentry in one of the following use-cases:
 
 - Browser Extensions