[8.1] Add release notes for 8.1.2

Co-authored-by: Seth Michael Larson <[email protected]>

Author: github-actions[bot]

docs/guide/release-notes.asciidoc

@@ -1,6 +1,7 @@
 [[release-notes]]
 == Release notes
 
+* <<rn-8-1-2>>
 * <<rn-8-1-1>>
 * <<rn-8-1-0>>
 * <<rn-8-0-0>>
@@ -41,6 +42,13 @@
 * <<rn-7-0-0>>
 
 
+[discrete]
+[[rn-8-1-2]]
+=== 8.1.2 (2022-03-30)
+
+* Client is compatible with Elasticsearch 8.1.2
+
+
 [discrete]
 [[rn-8-1-1]]
 === 8.1.1 (2022-03-22)