Adds ParametricRoleHOW refs #1306

doc/Type/Metamodel/ParametricRoleHOW.pod6

@@ -0,0 +1,41 @@
+=begin pod
+
+=TITLE role Metamodel::ParametricRoleHOW
+
+=SUBTITLE Represents a non-instantiated, parametrized, role.
+
+    class Metamodel::ParametricRoleHOW
+        does Metamodel::Naming
+        does Metamodel::Documenting
+        does Metamodel::Versioning
+        does Metamodel::MethodContainer
+        does Metamodel::PrivateMethodContainer
+        does Metamodel::MultiMethodContainer
+        does Metamodel::AttributeContainer
+        does Metamodel::RoleContainer
+        does Metamodel::MultipleInheritance
+        does Metamodel::Stashing
+        does Metamodel::TypePretense
+        does Metamodel::RolePunning
+        does Metamodel::ArrayType {}
+
+A C<Metamodel::ParametricRoleHOW> represents a non-instantiated, possibly
+parametrized, role:
+
+=for code
+(role Zape[::T] {}).HOW.say;# OUTPUT: «Perl6::Metamodel::ParametricRoleHOW.new␤»
+(role Zape {}).HOW.say; # OUTPUT: «Perl6::Metamodel::ParametricRoleHOW.new␤»
+
+As usual, C<.new_type> will create a new object of this class.
+
+=for code
+my \zipi := Metamodel::ParametricRoleHOW.new_type( name => "zape", group => "Zape");
+say zipi.HOW; # OUTPUT: «Perl6::Metamodel::ParametricRoleHOW.new␤»
+
+The extra C<group> argument will need to be used to integrate it in a parametric
+role group, which will need to be defined in advance.
+
+I<Note>: As most of the C<Metamodel> classes, this class is here mainly for
+illustration purposes and it's not intended for the final user to instantiate.
+
+=end pod