fix: read_image and write_image now use LocalFileSystem as defa…

…ult (#140)

## 📥 Pull Request Description

Currently you cannot use `read_image` and `write_image` without
specifying a FileSystem. The default (`LocalFileSystem`) was not used
correctly. This is now fixed in this PR.

## 👀 Affected Areas

- ioutils

## 📝 Checklist

Please make sure you've completed the following tasks before submitting
this pull request:

- [X] Pre-commit hooks were executed
- [ ] Changes have been reviewed by at least one other developer
- [ ] Tests have been added or updated to cover the changes (only
necessary if the changes affect the executable code)
- [X] All tests ran successfully
- [X] All merge conflicts are resolved
- [X] Documentation has been updated to reflect the changes
- [X] Any necessary migrations have been run

niceml/utilities/ioutils.py

@@ -289,7 +289,7 @@ def write_image(
         dirname(filepath),
         exist_ok=True,
     )
-    with file_system.open(filepath, "wb") as file:
+    with cur_fs.open(filepath, "wb") as file:
         file_format = filepath.rsplit(".")[-1]
         image.save(file, format=file_format, **kwargs)
 
@@ -311,7 +311,7 @@ def read_image(
     cur_fs: AbstractFileSystem = file_system or LocalFileSystem()
     if not cur_fs.exists(filepath):
         raise FileNotFoundError(f"ImageFile not found: {filepath}")
-    with file_system.open(filepath, "rb") as file:
+    with cur_fs.open(filepath, "rb") as file:
         return Image.open(file, **kwargs).copy()