chore(github): update issue templates

.github/ISSUE_TEMPLATE/feature-request.yml

@@ -6,6 +6,15 @@ body:
     attributes:
       value: |
         Before requesting a feature, please make sure that you have read through our [documentation](https://ui.nuxt.com) and existing [issues](https://github.com/nuxt/ui/issues?q=is%3Aissue+is%3Aopen+sort%3Aupdated-desc).
+  - type: dropdown
+    id: version
+    attributes:
+      label: For what version of Nuxt UI are you suggesting this?
+      options:
+        - v2.x
+        - v3-alpha
+    validations:
+      required: true
   - type: textarea
     id: description
     attributes: