docs(xcat-core): the release table stops at 2.18.0

The release information page lists every release up to 2.18.0. 2.18.2,
2.19.0 and 2.19.1 are published and absent from it, so a reader cannot
tell from the documentation which releases exist, when each one shipped,
or where its notes are.

docs/source/overview/_files/2.19.x.csv is new and holds the 2.19.0 and
2.19.1 rows, xcat2_release.rst gains its section above 2.18.x, and
2.18.x.csv gains the 2.18.2 row. Each date is the date of that release
on GitHub. 2.18.1 has no GitHub release of its own, so it has no row.

Signed-off-by: Daniel Hilst <392820+dhilst@users.noreply.github.com>

docs/source/overview/_files/2.18.x.csv

@@ -1,2 +1,3 @@
 Version,Release Date,New OS Supported,Release Notes
+2.18.2,2026-08-01,,`2.18.2 Release Notes <https://github.com/xcat2/xcat-core/wiki/XCAT_2.18.2_Release_Notes>`_
 2.18.0,2026-06-22,"RHEL 10,AlmaLinux 10",`2.18.0 Release Notes <https://github.com/xcat2/xcat-core/wiki/XCAT_2.18_Release_Notes>`_

docs/source/overview/_files/2.19.x.csv

@@ -0,0 +1,3 @@
+Version,Release Date,New OS Supported,Release Notes
+2.19.1,2026-09-25,,`2.19.1 Release Notes <https://github.com/xcat2/xcat-core/wiki/XCAT_2.19.1_Release_Notes>`_
+2.19.0,2026-09-18,"Ubuntu 26.04, riscv64 on EL10, Ubuntu 24.04 and Ubuntu 26.04",`2.19.0 Release Notes <https://github.com/xcat2/xcat-core/wiki/XCAT_2.19_Release_Notes>`_

docs/source/overview/xcat2_release.rst

@@ -6,6 +6,15 @@ The following tables documents the xCAT release versions and release dates. For
 
 .. tabularcolumns:: |p{1cm}|p{4cm}|p{7cm}|p{7cm}
 
+xCAT 2.19.x
+-----------
+
+.. csv-table:: 2.19.x Release Information
+   :file: _files/2.19.x.csv
+   :header-rows: 1
+   :class: longtable
+   :widths: 1 1 1 1
+
 xCAT 2.18.x
 -----------