[DOCs] Adds ml-cpp PRs to alpha release notes (#36790)

docs/Versions.asciidoc

@@ -14,8 +14,9 @@ release-state can be: released | prerelease | unreleased
 :release-state:   prerelease
 
 :issue:           https://github.com/elastic/elasticsearch/issues/
+:ml-issue:        https://github.com/elastic/ml-cpp/issues/
 :pull:            https://github.com/elastic/elasticsearch/pull/
-
+:ml-pull:         https://github.com/elastic/ml-cpp/pull/
 :docker-repo:     docker.elastic.co/elasticsearch/elasticsearch
 :docker-image:    {docker-repo}:{version}
 :plugin_url:      https://artifacts.elastic.co/downloads/elasticsearch-plugins

docs/reference/release-notes/7.0.0-alpha1.asciidoc

@@ -29,4 +29,11 @@ Suggesters::
 * Plugins that register suggesters can now define their own types of suggestions and must
   explicitly indicate the type of suggestion that they produce. Existing plugins will
   require changes to their plugin registration. See the `custom-suggester` example
-  plugin {pull}30284[#30284]
+  plugin {pull}30284[#30284]
+  
+[float]
+[[enhancement-7.0.0-alpha1]]
+=== Enhancements
+
+Machine learning::
+* Adds categorical filter type to detector rules. {ml-pull}27[#27]

docs/reference/release-notes/7.0.0-alpha2.asciidoc

@@ -2,3 +2,9 @@
 == {es} version 7.0.0-alpha2
 
 coming[7.0.0-alpha2]
+
+[float]
+[[bug-7.0.0-alpha2]]
+=== Bug fixes
+
+* Fixes CPoissonMeanConjugate sampling error. {ml-pull}335[#335]