add test txt2txt model to constants

skynet/constants.py

@@ -14,7 +14,7 @@ class Size(msgspec.Struct):
 class ModelDesc(msgspec.Struct):
     short: str
     mem: float
-    size: Size
+    size: Size | None
     tags: list[Literal['txt2img', 'img2img', 'inpaint']]
 
 MODELS: dict[str, ModelDesc] = {
@@ -78,6 +78,12 @@ MODELS: dict[str, ModelDesc] = {
         size=Size(w=512, h=512),
         tags=['txt2img']
     ),
+    'microsoft/DialoGPT-small': ModelDesc(
+        short='dgpt-sm',
+        mem=6,
+        size=None,
+        tags=['txt2txt']
+    ),
     'diffusers/stable-diffusion-xl-1.0-inpainting-0.1': ModelDesc(
         short='stablexl-inpainting',
         mem=8.3,