Use imageio instead of matplotlib to generate image.

src/holt59/aoc/base.py

@@ -1,5 +1,6 @@
 from abc import abstractmethod
 from logging import Logger
+from pathlib import Path
 from typing import Any, Final, Iterable, Iterator, Protocol, Sequence, TypeVar, overload
 
 from numpy.typing import NDArray
@@ -22,10 +23,10 @@ class FileHandler:
     def image(self, filename: str, image: NDArray[Any]):
         from io import BytesIO
 
-        import matplotlib.pyplot as plt
+        import imageio.v3 as iio
 
         io = BytesIO()
-        plt.imsave(io, image)  # type: ignore
+        iio.imwrite(io, image, extension=Path(filename).suffix)  # type: ignore
         io.seek(0)
 
         self.create(filename, io.read(), False)