Fixed type checking error

The use of an ellipsis in type annotation was not allowed when testing this program on linux. It has been replaced with NoneType.

src/custom_types.py

@@ -8,7 +8,7 @@ class Placement(TypedDict):
     word: str
     direction: str
     pos: Tuple[int]
-    intersections: Union[List[...], List[Tuple[int]]]
+    intersections: Union[List[None], List[Tuple[int]]]
 
 class CrosswordData(TypedDict):
     '''The JSON serialised definitions and info of a base crossword.'''

src/cword_gen.py

@@ -148,7 +148,7 @@ def _find_intersections(self,
                             direction: str, 
                             row: int, 
                             column: int
-                            ) -> Union[Tuple[...], Tuple[int]]:
+                            ) -> Union[Tuple[None], Tuple[int]]:
         '''Find the row and column of all points of intersection that the `word` has with the `self.grid`.'''
         intersections = list()