chore: contains_key needs a Box<str>, so generify is_dir to accept one

src/read.rs

@@ -703,6 +703,7 @@ impl<R: Read + Seek> ZipArchive<R> {
                                 "Invalid UTF-8 as symlink target",
                             ));
                         };
+                        let target = target.into_boxed_str();
                         let target_is_dir_from_archive =
                             self.shared.files.contains_key(&target) && is_dir(&target);
                         let target_internal_path: PathBuf = target.into();

src/spec.rs

@@ -227,7 +227,7 @@ impl Zip64CentralDirectoryEnd {
     }
 }
 
-pub(crate) fn is_dir(filename: &str) -> bool {
+pub(crate) fn is_dir<T: AsRef<str>>(filename: T) -> bool {
     filename
         .chars()
         .next_back()