SPath: Add append_to_stem

Append a list of suffixes to the current stem. This is mainly meant to be a convenience method for stuff like iterating over a list and storing the index in the filepath to disambiguate between files.

append_to_stem: `"` -> `'`

append_to_stem: Use to_arr

append_to_stem: list -> Iterable

append_to_stem: Add sep param

stgpytools/types/file.py

@@ -4,6 +4,8 @@
 from pathlib import Path
 from typing import TYPE_CHECKING, Any, Callable, Iterable, Literal, TypeAlias, Union
 
+from ..functions import to_arr
+
 __all__ = [
     'FilePathType', 'FileDescriptor',
     'FileOpener',
@@ -99,5 +101,10 @@ def write_lines(
     ) -> int:
         return super().write_text('\n'.join(data), encoding, errors, newline)
 
+    def append_to_stem(self, suffixes: str | Iterable[str], sep: str = '_') -> SPath:
+        """Append a suffix to the stem of the path"""
+
+        return self.with_stem(sep.join([self.stem, *to_arr(suffixes)]))  # type:ignore[list-item]
+
 
 SPathLike = Union[str, Path, SPath]