improve start/end typing

discord/models.py

@@ -1,4 +1,4 @@
-from pydantic import BaseModel
+from pydantic import BaseModel, NonNegativeInt
 from pypresence.types import ActivityType
 from typing import Optional
 
@@ -9,6 +9,6 @@ class DiscordRPCUpdatePayload(BaseModel):
     subtitle: str
     image_url: str
     details: str
-    start: Optional[int]
-    end: Optional[int]
+    start: Optional[NonNegativeInt]
+    end: Optional[NonNegativeInt]
     activity_type: ActivityType