test(android_strings, placeholder): add tests for non-ASCII strings

- Added a test case in `placeholder.rs` to validate the signature extraction for a Chinese string.
- Updated `android_strings.rs` to include a non-ASCII string in the XML format and adjusted the expected string count and assertions accordingly.

Author: WendellXY

langcodec/src/formats/android_strings.rs

@@ -429,10 +429,11 @@ mod tests {
             <string name="multiple_lines">Hello\n\n
 World
             </string>
+            <string name="some_non_ascii">你好</string>
         </resources>
         "#;
         let format = Format::from_str(xml).unwrap();
-        assert_eq!(format.strings.len(), 4);
+        assert_eq!(format.strings.len(), 5);
         let hello = &format.strings[0];
         assert_eq!(hello.name, "hello");
         assert_eq!(hello.value, "Hello");
@@ -449,6 +450,10 @@ World
         assert_eq!(multiple_lines.name, "multiple_lines");
         assert_eq!(multiple_lines.value, r#"Hello\n\n\nWorld\n    "#);
         assert_eq!(multiple_lines.translatable, None);
+        let some_non_ascii = &format.strings[4];
+        assert_eq!(some_non_ascii.name, "some_non_ascii");
+        assert_eq!(some_non_ascii.value, "你好");
+        assert_eq!(some_non_ascii.translatable, None);
     }
 
     #[test]

langcodec/src/placeholder.rs

@@ -228,6 +228,9 @@ mod tests {
         let s = "Hello %1$@, you have %2$d items and %s extra";
         let sig = signature(s);
         assert_eq!(sig, vec!["1$s", "2$d", "s"]);
+        let s = "你好,%s";
+        let sig = signature(s);
+        assert_eq!(sig, vec!["s"]);
     }
 
     #[test]