Windows support

Books.py

@@ -207,7 +207,7 @@ def RenameFile(SourcePath: Path, NewName: str) -> Path:
     """Renames a file and its Book together; undoes the file rename if the
     Book can't follow. Returns the new path."""
     NewName = NewName.strip()
-    if not NewName or "/" in NewName or NewName in (".", ".."):
+    if not NewName or "/" in NewName or "\\" in NewName or NewName in (".", ".."):
         raise DataError("That isn't a valid file name.")
     if NewName.startswith("."):
         raise DataError("Names starting with a dot are hidden, and SaraTag skips hidden files.")