Add 8.16 release notes (#2405)

Add 8.16 release notes

docs/release-notes/8.16.asciidoc

@@ -0,0 +1,38 @@
+[[ecs-release-notes-8.16.0]]
+=== 8.16.0
+
+[[schema-changes-8.16.0]]
+[float]
+==== Schema changes
+
+[[schema-bugfixes-8.16.0]]
+[float]
+===== Bugfixes
+* Fix broken link in docs for vulnerability.id. {ecs_pull}2328[#2328]
+
+[[schema-added-8.16.0]]
+[float]
+===== Added
+
+* Added `volume.*` as beta field set. {ecs_pull}2269[#2269]
+* Advanced `process.env_vars` to GA. {ecs_pull}2315[#2315]
+* Advanced `process.io` and `process.tty` fields to GA. {ecs_pull}2317[#2317]
+* Added `threat.indicator.id`. {ecs_pull}2324[#2324]
+* Added `process.group` to generated schemas. {ecs_pull}2335[#2335]
+
+
+[[tooling-changes-8.16.0]]
+[float]
+==== Tooling and artifact changes
+
+[[tooling-bugfixes-8.16.0]]
+[float]
+===== Bugfixes
+* Fix broken link for vulnerabilty.id {ecs_pull}2328[#2328]
+
+[[tooling-added-8.16.0]]
+[float]
+===== Added
+
+* Documentation in README.md providing instruction on contributions to ECS during the OTel donation {ecs_pull}2325[#2325]
+

docs/release-notes/index.asciidoc

@@ -3,6 +3,7 @@
 
 This section summarizes the changes in each release.
 
+* <<ecs-release-notes-8.16.0, {ecs} version 8.16.0>>
 * <<ecs-release-notes-8.11.0, {ecs} version 8.11.0>>
 * <<ecs-release-notes-8.10.0, {ecs} version 8.10.0>>
 * <<ecs-release-notes-8.9.0, {ecs} version 8.9.0>>
@@ -27,6 +28,7 @@ This section summarizes the changes in each release.
 :issue: https://github.com/elastic/ecs/issues/
 :pull: https://github.com/elastic/ecs/pull/
 
+include::8.16.asciidoc[]
 include::8.11.asciidoc[]
 include::8.10.asciidoc[]
 include::8.9.asciidoc[]