add utils.parse.try_int() because .isdigit() isnt good enough

src/utils/parse.py

@@ -73,3 +73,9 @@ def keyvalue(s: str, delimiter: str=" "
         else:
             items[key] = None
     return items
+
+def try_int(s: str) -> typing.Optional[int]:
+    try:
+        return int(s)
+    except ValueError:
+        return None