feat/stubgen: add const and generic support

src/capnp_stubgen/plugin.py

@@ -16,6 +16,7 @@ import sys
 from typing import TYPE_CHECKING
 
 from .emitter import Emitter
+from .gen_const import generate_const
 from .gen_enum import generate_enum
 from .gen_struct import generate_struct
 from .models import TypeRegistry
@@ -119,5 +120,7 @@ def _generate_file(
             generate_enum(emitter, type_info)
         elif type_info.kind == "struct":
             generate_struct(emitter, type_info, registry)
+        elif type_info.kind == "const":
+            generate_const(emitter, type_info, registry)
 
     return emitter.render()