releases: update to include 3.1.9

    Adding 3.1.9 to documentation switcher and release list.

(From yocto-docs rev: 6951b86a2e0e95bb72db12624efa23fec579bc70)

Signed-off-by: Michael Halstead <mhalstead@linuxfoundation.org>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

documentation/releases.rst

@@ -34,6 +34,7 @@ Release Series 3.1 (dunfell)
 - :yocto_docs:`3.1.6 Documentation </3.1.6>`
 - :yocto_docs:`3.1.7 Documentation </3.1.7>`
 - :yocto_docs:`3.1.8 Documentation </3.1.8>`
+- :yocto_docs:`3.1.8 Documentation </3.1.9>`
 
 ==========================
  Outdated Release Manuals

documentation/sphinx-static/switchers.js

@@ -5,7 +5,7 @@
     'dev': 'dev (3.4)',
     '3.3.1': '3.3.1',
     '3.2.4': '3.2.4',
-    '3.1.8': '3.1.8',
+    '3.1.9': '3.1.9',
     '3.0.4': '3.0.4',
     '2.7.4': '2.7.4',
   };