fix(#3940): Add release navigation links to _index.md

- Fixed 'file not found' error in releases directory
- Added navigation links for Kubeflow 0.6-1.9
- Verified diff shows all 12 links added
- Closes #3940

Author: Sapthagiri777

content/en/docs/kubeflow-platform/releases/_index.md

@@ -3,3 +3,19 @@ title = "Releases"
 description = "Information about past and future Kubeflow AI reference platform releases"
 weight = 100
 +++
+
+## Kubeflow Releases
+
+- [Kubeflow 1.9](kubeflow-1.9.md)
+- [Kubeflow 1.8](kubeflow-1.8.md)
+- [Kubeflow 1.7](kubeflow-1.7.md)
+- [Kubeflow 1.6](kubeflow-1.6.md)
+- [Kubeflow 1.5](kubeflow-1.5.md)
+- [Kubeflow 1.4](kubeflow-1.4.md)
+- [Kubeflow 1.3](kubeflow-1.3.md)
+- [Kubeflow 1.2](kubeflow-1.2.md)
+- [Kubeflow 1.1](kubeflow-1.1.md)
+- [Kubeflow 1.0](kubeflow-1.0.md)
+- [Kubeflow 0.7](kubeflow-0.7.md)
+- [Kubeflow 0.6](kubeflow-0.6.md)
+