chore: add missing READMEs and fix clippy warning

Add README files for common, jni-bridge, and shuffle crates.
Add Default impl for Recorder to satisfy clippy.

Author: andygrove

native/common/README.md

@@ -0,0 +1,25 @@
+<!--
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements.  See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership.  The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License.  You may obtain a copy of the License at
+
+  http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied.  See the License for the
+specific language governing permissions and limitations
+under the License.
+-->
+
+# datafusion-comet-common: Common Types
+
+This crate provides common types shared across Apache DataFusion Comet crates and is maintained as part of the
+[Apache DataFusion Comet] subproject.
+
+[Apache DataFusion Comet]: https://github.com/apache/datafusion-comet/

native/common/src/tracing.rs

@@ -29,6 +29,12 @@ pub struct Recorder {
     writer: Arc<Mutex<BufWriter<File>>>,
 }
 
+impl Default for Recorder {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
 impl Recorder {
     pub fn new() -> Self {
         let file = OpenOptions::new()

native/jni-bridge/README.md

@@ -0,0 +1,25 @@
+<!--
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements.  See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership.  The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License.  You may obtain a copy of the License at
+
+  http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied.  See the License for the
+specific language governing permissions and limitations
+under the License.
+-->
+
+# datafusion-comet-jni-bridge: JNI Bridge
+
+This crate provides the JNI interaction layer for Apache DataFusion Comet and is maintained as part of the
+[Apache DataFusion Comet] subproject.
+
+[Apache DataFusion Comet]: https://github.com/apache/datafusion-comet/

native/shuffle/README.md

@@ -0,0 +1,25 @@
+<!--
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements.  See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership.  The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License.  You may obtain a copy of the License at
+
+  http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied.  See the License for the
+specific language governing permissions and limitations
+under the License.
+-->
+
+# datafusion-comet-shuffle: Shuffle Writer and Reader
+
+This crate provides the shuffle writer and reader implementation for Apache DataFusion Comet and is maintained as part
+of the [Apache DataFusion Comet] subproject.
+
+[Apache DataFusion Comet]: https://github.com/apache/datafusion-comet/