Add missed spec version 1.12 in the sdf_descriptions target (#1529)

This also updates the default versions in root.sdf files

Signed-off-by: Addisu Z. Taddese <addisu@openrobotics.org>
(cherry picked from commit fd0292a)

# Conflicts:
#	sdf/1.12/root.sdf

sdf/1.11/root.sdf

@@ -1,7 +1,7 @@
 <element name="sdf" required="1">
   <description>SDFormat base element that can include one model, actor, light, or worlds. A user of multiple worlds could run parallel instances of simulation, or offer selection of a world at runtime.</description>
 
-  <attribute name="version" type="string" default="1.10" required="1">
+  <attribute name="version" type="string" default="1.11" required="1">
     <description>
         Version number of the SDFormat specification, consisting of major
         and minor versions delimited by a `.` character.

sdf/1.12/root.sdf

@@ -0,0 +1,21 @@
+<element name="sdf" required="1">
+  <description>SDFormat base element that can include one model, actor, light, or worlds. A user of multiple worlds could run parallel instances of simulation, or offer selection of a world at runtime.</description>
+
+  <attribute name="version" type="string" default="1.12" required="1">
+    <description>
+        Version number of the SDFormat specification, consisting of major
+        and minor versions delimited by a `.` character.
+        A major version bump is required if older versions cannot be
+        automatically converted to this version.
+        A minor version bump is required when there are breaking changes that
+        can be handled by the automatic conversion functionality encoded in the
+        `*.convert` files.
+    </description>
+  </attribute>
+
+  <include filename="world.sdf" required="*"/>
+  <include filename="model.sdf" required="0"/>
+  <include filename="actor.sdf" required="0"/>
+  <include filename="light.sdf" required="0"/>
+
+</element> <!-- End SDF -->

sdf/CMakeLists.txt

@@ -31,7 +31,7 @@ execute_process(
 if (GZ_PROGRAM)
 
   # Update this list as new sdformat spec versions are added.
-  set(sdf_desc_versions 1.4 1.5 1.6 1.7 1.8 1.9 1.10 1.11)
+  set(sdf_desc_versions 1.4 1.5 1.6 1.7 1.8 1.9 1.10 1.11 1.12)
 
   set(description_targets)
   foreach(desc_ver ${sdf_desc_versions})