Merge #4665

4665: Add missing Korean support r=ManyTheFish a=junhochoi

Some configuration is missing `korean` features and add a test case in `milli/src/search/mod.rs`.

# Pull Request

## Related issue

#3443 #3882 

## What does this PR do?
- Improvement on enabling Korean support

Inspired by the work (#3882) I tried to enable Korean features but have found some missing configurations.
This PR is add those missing configs (mostly Cargo.toml) and added one test case.

## PR checklist
Please check if your PR fulfills the following requirements:
- [x] Does this PR fix an existing issue, or have you listed the changes applied in the PR description (and why they are needed)?
- [x] Have you read the contributing guidelines?
- [x] Have you made sure that the title is accurate and descriptive of the changes?

Thank you so much for contributing to Meilisearch!


Co-authored-by: Junho Choi <jh.choi@catenoid.net>

milli/src/search/mod.rs

@@ -336,4 +336,28 @@ mod test {
 
         assert_eq!(documents_ids, vec![1]);
     }
+
+    #[cfg(feature = "korean")]
+    #[test]
+    fn test_hangul_language_detection() {
+        use crate::index::tests::TempIndex;
+
+        let index = TempIndex::new();
+
+        index
+            .add_documents(documents!([
+                { "id": 0, "title": "The quick (\"brown\") fox can't jump 32.3 feet, right? Brr, it's 29.3°F!" },
+                { "id": 1, "title": "김밥먹을래。" },
+                { "id": 2, "title": "הַשּׁוּעָל הַמָּהִיר (״הַחוּם״) לֹא יָכוֹל לִקְפֹּץ 9.94 מֶטְרִים, נָכוֹן? ברר, 1.5°C- בַּחוּץ!" }
+            ]))
+            .unwrap();
+
+        let txn = index.write_txn().unwrap();
+        let mut search = Search::new(&txn, &index);
+
+        search.query("김밥");
+        let SearchResult { documents_ids, .. } = search.execute().unwrap();
+
+        assert_eq!(documents_ids, vec![1]);
+    }
 }