patch 9.0.2076: Vim9: No support for type aliases

Problem:  Vim9: No support for type aliases
Solution: Implement :type command

A type definition is giving a name to a type specification.  This also known
type alias.

	:type ListOfStrings = list<string>

The type alias can be used wherever a built-in type can be used.  The type
alias name must start with an upper case character.

closes: #13407

Signed-off-by: Christian Brabandt <cb@256bit.org>
Signed-off-by: Yegappan Lakshmanan <yegappan@yahoo.com>
diff --git a/src/if_py_both.h b/src/if_py_both.h
index 0620171..f843863 100644
--- a/src/if_py_both.h
+++ b/src/if_py_both.h
@@ -6772,6 +6772,7 @@
 	case VAR_INSTR:
 	case VAR_CLASS:
 	case VAR_OBJECT:
+	case VAR_TYPEALIAS:
 	    Py_INCREF(Py_None);
 	    return Py_None;
 	case VAR_BOOL: