Add unmaintained notice to contrib tektoncd (kubeflow#2321)

* Add unmaintained notice to contrib tektoncd

Signed-off-by: Anna Jung (VMware) <antheaj@vmware.com>

* Update contrib/tektoncd/README.md

Co-authored-by: Tommy Li <Tommy.chaoping.li@ibm.com>

* Update message

Signed-off-by: Anna Jung (VMware) <antheaj@vmware.com>

Signed-off-by: Anna Jung (VMware) <antheaj@vmware.com>
Co-authored-by: Tommy Li <Tommy.chaoping.li@ibm.com>

contrib/tektoncd/README.md

@@ -0,0 +1,8 @@
+Please note: This component is **unmaintained and out-of-date**.
+
+The latest tektoncd distribution is now maintained as part of the `kfp-tekton` component release. To deploy tektoncd standalone with kustomize, please use the latest tektoncd kustomization.yaml over [here](/apps/kfp-tekton/upstream/third-party/tekton/base/kustomization.yaml).
+
+Any components that fails to meet [contrib requirements](https://github.com/kubeflow/manifests/blob/master/proposals/20220926-contrib-component-guidelines.md#component-requirements)
+ by the next Kubeflow release ([1.7](https://github.com/kubeflow/community/tree/master/releases/release-1.7#timeline)) will be removed from the [`manifest`](https://github.com/kubeflow/manifests) repository.
+
+Updates to the `/contrib` components can be found in the [tracking issue](https://github.com/kubeflow/manifests/issues/2311).