Update README.md

update the readme file, add write and read example.

Author: baifachuan

Diff for: README.md

@@ -36,4 +36,46 @@ but we need:
 ...
 ```
 
-more info and cn version to see: https://baifachuan.com/posts/2e6dc139.html
+the example for read in : com.fcbai.parquet.sdk.CustomParquetReaderTest
+```java
+@Test
+public void test_read_complex_map_partition_table_content() throws IOException {
+    ParquetReader<CustomSimpleRecord> reader = ParquetReader
+            .builder(new CustomSimpleReadSupport(), new Path(complexMapFilepath))
+            .withFilter(FilterCompat.get(page(1, 10)))
+            .build();
+    for (CustomSimpleRecord value = reader.read(); value != null; value = reader.read()) {
+        System.out.println(value.toJson());
+    }
+    reader.close();
+}
+```
+
+the write example:
+
+```java
+@Test
+public void test_write_to_parquet_by_java() throws IOException {
+    List<User> users = new ArrayList<>();
+    User user1 = new User("1","fcbai","123123");
+    User user2 = new User("2","fcbai","123445");
+    users.add(user1);
+    users.add(user2);
+    Path dataFile = new Path("./src/test/resources/demo.snappy.parquet");
+    // Write as Parquet file.
+    try (ParquetWriter<User> writer = AvroParquetWriter.<User>builder(dataFile)
+            .withSchema(ReflectData.AllowNull.get().getSchema(User.class))
+            .withDataModel(ReflectData.get())
+            .withConf(new Configuration())
+            .withCompressionCodec(SNAPPY)
+            .withWriteMode(OVERWRITE)
+            .build()) {
+        for (User user : users) {
+            writer.write(user);
+        }
+    }
+}
+```
+
+
+more info and cn version to see: https://baifachuan.com/posts/2e6dc139.html