add ScyllaDB Enterprise Version Support page

This PR moves the version support page for Enterprise from the Enterprise repo (versioned) to this repo (unversioned).
Refs scylladb/scylla-enterprise#4607

docs/index.rst

@@ -164,4 +164,5 @@
 .. toctree::
    :hidden:
 
-   get-started/index
+   get-started/index
+   versioning/index 

docs/versioning/index.rst

@@ -0,0 +1,8 @@
+==============================
+Versioning and Support Policy
+==============================
+
+.. toctree::
+   :maxdepth: 1
+
+   version-support-enterprise

docs/versioning/version-support-enterprise.rst

@@ -0,0 +1,110 @@
+======================================
+ScyllaDB Enterprise Version Support 
+======================================
+
+Supported Versions
+------------------------
+
+.. list-table:: 
+   :widths: 20 25 20 35
+   :header-rows: 1
+
+   * - Version
+     - Released
+     - Status
+     - End of Life (EOL)
+   * - 2024.2
+     - September 2024
+     - Supported
+     - After 2026.1 or 2025.2 is released (see :ref:`Version Support Policy <version-support-policy>`)
+   * - 2024.1 (LTS)
+     - February 2024
+     - Supported
+     - After 2026.1 is released (see :ref:`Version Support Policy <version-support-policy>`)
+   * - 2023.1 (LTS)
+     - August 2023
+     - Supported
+     - After 2025.1 is released (see :ref:`Version Support Policy <version-support-policy>`)
+   * - 2022.2
+     - January 2023
+     - Not supported
+     - June 2024
+   * - 2022.1 (LTS)
+     - August 2022
+     - Not supported
+     - June 2024
+
+Version Numbering
+-------------------
+
+ScyllaDB Enterprise follows the MAJOR.MINOR.PATCH `semantic versioning <https://semver.org/>`_:
+
+* ``MAJOR`` versions contain significant changes in the product and may
+  introduce incompatible API changes.
+* ``MINOR`` versions introduce new features and improvements in a backward-compatible manner.
+* ``PATCH`` versions have backward-compatible bug fixes.
+
+.. image:: images/enterprise-versioning.png
+    :width: 300px
+
+LTS vs. Feature Releases
+----------------------------
+
+Long-Term Support (LTS)
+
+* Released approximately once a year.
+* Two last LTS versions are supported.
+
+Feature releases:
+
+* 2-4 feature releases per year.
+* Closely follow ScyllaDB Open Source releases
+  (see `ScyllaDB Enterprise vs. Open Source Matrix <https://enterprise.docs.scylladb.com/stable/reference/versions-matrix-enterprise-oss.html>`_).
+* Introduce features added in ScyllaDB Open Source, as well as Enterprise-only
+  features.
+
+You can only use LTS releases (upgrading to the latest patch release for
+the greatest stability) or follow the feature and LTS releases for the latest
+feature set.
+
+*An illustrative example:*
+
+.. image:: images/lts-feature-lane.png
+     :width: 600px
+
+
+.. _version-support-policy:
+
+Version Support Policy
+-------------------------
+
+* The last two LTS versions are supported.
+* The last two *major.minor* versions (Feature or LTS release) are supported.
+
+**Example**
+
+* When 2024.2 (Feature) is released, the following are supported:
+
+  * 2024.1 and 2023.1 (the last two LTS)
+  * 2024.2 (Feature) and 2024.1 (LTS)
+
+* When 2025.1 (LTS) is released, the following are supported:
+
+  * 2025.1 and 2024.1 (the last two LTS)
+  * 2024.2 (Feature)
+
+* When 2025.2 (Feature) is released, the following are supported: 
+
+  * 2025.1 and 2024.1 (the last two LTS)
+  * 2025.2 (Feature)
+
+
+Patch Versions
+================
+
+All supported versions (major and minor, LTS and Feature) will get patch
+releases when required.
+
+We recommend upgrading to the latest patch version. You should especially
+upgrade to the latest patch of your current version before upgrading to
+a new major or minor version.