Add new file

doc/api/version-get.json

+{
+    "name": "version-get",
+    "brief": "The version-get command returns on the control channel what the command line -v argument displays with in arguments the extended version, i.e., what the command line -V argument displays.",
+    "description": "See <xref linkend=\"command-version-get\"/>",
+    "support": [ "kea-dhcp4", "kea-dhcp6" ],
+    "avail": "1.2.0",
+    "cmd-syntax": "{
+    \"command\": \"version-get\"
+}",
+}
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