Mark quaternion type as private (#12)

Per #11 change to mark `quaternion` type as private to omit it from document generation

Author: Martin-Pitt

lsl_definitions.yaml

@@ -11976,6 +11976,7 @@ types:
       surrounding their elements; the elements inside are separated by commas. e.g.
       [0, 1, 2, 3, 4] or ["Yes", "No", "Perhaps"].
   quaternion:
+    private: true
     tooltip: The quaternion type is a left over from way back when LSL was created.
       It was later renamed to <rotation> to make it more user friendly, but it appears
       someone forgot to remove it ;-)