feat: specify PDL types in the AST (#942)

Signed-off-by: Louis Mandel <[email protected]>

Author: mandel

examples/tutorial/type_list.pdl

@@ -2,5 +2,3 @@
 description: test
 spec: {"list": {"minItems": 0, "maxItems": 0, "str": {}}}
 data: ["hello", "world"]
-  
-