Add 21.2.0 release notes

source/partials/release_notes/_release-21-2-0.md.erb

@@ -0,0 +1,34 @@
+<h4>Changes</h4>
+
+* <%= link_to_issue 9086, 'Bundle latest Java 15' %>
+* Starting this release, Alpine 3.13 based docker images for GoCD Agent are <%= link_to 'available', 'https://hub.docker.com/r/gocd/gocd-agent-alpine-3.13' %>.
+
+<h4>Bug fixes</h4>
+
+* <%= link_to_issue 8899, '"Config Changed" diff marks lines containing dash (`-`) as removed' %>
+* <%= link_to_issue 9073, 'Add missing Content-Type check' %>
+
+<h4>APIs</h4>
+
+Improvements, deprecations and breaking changes in the API and plugin API have been moved to their respective changelogs - <%= link_to_versioned_api '21.2.0','changes-in-21-2-0', 'API changelog for 21.2.0' %> and <%= link_to_versioned_plugin_api '21.2.0','changes-in-gocd-21-2-0', 'Plugin API changelog for 21.2.0' %>.
+
+<h4>Contributors</h4>
+
+<%= [
+  "Aravind SV",
+  "Ganesh S Patil",
+  "Ketan Padegaonkar",
+  "Kritika Singh",
+  "Mahesh Panchaksharaiah",
+  "Marques Lee",
+  "Varsha Varadarajan",
+].sort.uniq.join(', ')
+%>
+
+<h4>Note</h4>
+
+A more comprehensive list of changes for this release can be found <%= link_to_full_changelog 'here.', 'Release 21.2.0' %>
+
+Found a security issue that needs fixing? Please report it to <%= link_to 'https://hackerone.com/gocd', 'https://hackerone.com/gocd' %>
+
+Please report any issues that you observe on [GitHub issues](https://github.com/gocd/gocd/issues).