use cross-platform path separator

Author: hatemhosny

scripts/fetch-algorithms.ts

@@ -550,10 +550,10 @@ const categoriesToSkip = ["main", "src", "algorithms", "problems"];
 function isValidCategory(name: string) {
   if (normalize(name).match(/problem\d+/)) return false;
   for (const exclude of categoriesToIgnore)
-    for (const category of name.split("/"))
+    for (const category of name.split(path.sep))
       if (normalize(category) === normalize(exclude)) return false;
   for (const exclude of ["__init__", "mod.rs"])
-    for (const category of name.split("/"))
+    for (const category of name.split(path.sep))
       if (category === exclude) return false;
   return true;
 }