Allow interpreted subclasses

Author: GlassOfWhiskey

setup.py

@@ -50,8 +50,10 @@
         "src/schema_salad/jsonld_context.py",
         "src/schema_salad/main.py",
         "src/schema_salad/makedoc.py",
+        "src/schema_salad/metaschema.py",
         "src/schema_salad/python_codegen.py",
         "src/schema_salad/ref_resolver.py",
+        "src/schema_salad/runtime.py",
         "src/schema_salad/schema.py",
         "src/schema_salad/sourceline.py",
         "src/schema_salad/typescript_codegen.py",