Mark graceful node shutdown KEP as implementable

* Add alpha graduation criteria
* Update implementation history

Author: bobbypage

keps/sig-node/2000-graceful-node-shutdown/README.md

@@ -94,6 +94,7 @@ tags, and then generate with `hack/update-toc.sh`.
 - [Design Details](#design-details)
   - [Test Plan](#test-plan)
   - [Graduation Criteria](#graduation-criteria)
+    - [Alpha Graduation](#alpha-graduation)
     - [Alpha -> Beta Graduation](#alpha---beta-graduation)
     - [Beta -> GA Graduation](#beta---ga-graduation)
   - [Upgrade / Downgrade Strategy](#upgrade--downgrade-strategy)
@@ -129,12 +130,12 @@ checklist items _must_ be updated for the enhancement to be released.
 
 Items marked with (R) are required *prior to targeting to a milestone / release*.
 
-- [ ] (R) Enhancement issue in release milestone, which links to KEP dir in [kubernetes/enhancements] (not the initial KEP PR)
-- [ ] (R) KEP approvers have approved the KEP status as `implementable`
-- [ ] (R) Design details are appropriately documented
-- [ ] (R) Test plan is in place, giving consideration to SIG Architecture and SIG Testing input
-- [ ] (R) Graduation criteria is in place
-- [ ] (R) Production readiness review completed
+- [x] (R) Enhancement issue in release milestone, which links to KEP dir in [kubernetes/enhancements] (not the initial KEP PR)
+- [x] (R) KEP approvers have approved the KEP status as `implementable`
+- [x] (R) Design details are appropriately documented
+- [x] (R) Test plan is in place, giving consideration to SIG Architecture and SIG Testing input
+- [x] (R) Graduation criteria is in place
+- [x] (R) Production readiness review completed
 - [ ] Production readiness review approved
 - [ ] "Implementation History" section is up-to-date for milestone
 - [ ] User-facing documentation has been created in [kubernetes/website], for publication to [kubernetes.io]
@@ -560,6 +561,11 @@ in back-to-back releases.
 [conformance tests]: https://git.k8s.io/community/contributors/devel/sig-architecture/conformance-tests.md
 -->
 
+#### Alpha Graduation
+
+* Implemented the feature for Linux (systemd) only
+* Unit tests
+
 #### Alpha -> Beta Graduation
 
 * Addresses feedback from alpha testers
@@ -841,6 +847,8 @@ Major milestones might include:
 
 *   May 26 - [Original GH issue #91472
     filed](https://github.com/kubernetes/kubernetes/issues/91472)
+*   October 2 - [Initial KEP
+    approved](https://github.com/kubernetes/enhancements/pull/2001)
 
 ## Drawbacks