add new version guide

Signed-off-by: bmorelli25 <[email protected]>

Author: bmorelli25

docs/_docset.yml

@@ -37,6 +37,7 @@ toc:
       - file: cumulative-docs.md
       - file: branching-strategy.md
       - file: add-repo.md
+      - file: release-new-version.md
   - folder: migration
     children:
       - file: index.md

docs/contribute/release-new-version.md

@@ -0,0 +1,59 @@
+# Release a new documentation version
+
+When a new version of the Elastic Stack (or another versioned product) is released, the docs site must be updated to recognize it. This process primarily involves updating version metadata in the shared site configuration.
+
+Follow these steps to release a new documentation version.
+
+:::::{stepper}   
+
+::::{step} Update `versions.yml`
+
+The `versions.yml` file defines the **base** (minimum) and **current** (latest) versions of each versioned product family.
+
+Example:
+
+```yaml
+versioning_systems:
+  stack: &stack
+    base: 9.0
+    current: 9.1.0
+```
+
+- Update the `current` version to reflect the newly released version.
+- Only update the `base` version if you're dropping support for an older version.
+
+Refer to [`versions.yml`](../configure/site/versions.md) for more information.
+
+::::
+
+::::{step} (Optional) Update legacy URL mappings
+
+If you're releasing a version older than the current `base`, or restoring support for a previously removed version, you may need to update the `legacy-url-mappings.yml` file.
+
+This file maps legacy URL paths (like `en/elasticsearch/reference/`) to the list of versions that exist at that path.
+
+For example, to release a new 8.19 version of the Elastic Stack:
+
+```diff
+- stack: &stack [ '9.0+', '8.18', '8.17', '8.16', '8.15', '8.14', '8.13', '8.12', '8.11', '8.10', '8.9', '8.8', '8.7', '8.6', '8.5', '8.4', '8.3', '8.2', '8.1', '8.0', '7.17' ]
++ stack: &stack [ '9.0+', '8.19', '8.18', '8.17', '8.16', '8.15', '8.14', '8.13', '8.12', '8.11', '8.10', '8.9', '8.8', '8.7', '8.6', '8.5', '8.4', '8.3', '8.2', '8.1', '8.0', '7.17' ]
+```
+
+See [`legacy-url-mappings.yml`](../configure/site/legacy-url-mappings.md) for more information.
+
+::::
+
+::::{step} Release a new version of docs-builder
+
+Version updates and content set additions require a release of docs-builder.
+Contact the Docs Eng team for assistance.
+
+::::
+
+::::{step} Confirm `applies_to` metadata
+
+Cumulative documentation relies on version metadata through `applies_to` blocks, which use version definitions in `versions.yml`.
+
+Check the built output to ensure `applies_to` changes are correctly rendering.
+
+::::