[doc] Add VARIANT type in data-types

Author: JingsongLi

docs/content/concepts/data-types.md

@@ -175,6 +175,13 @@ All data types supported by Paimon are as follows:
           <code>The type can be declared using ROW&lt;n0 t0 'd0', n1 t1 'd1', ...&gt; where n is the unique name of a field, t is the logical type of a field, d is the description of a field.</code>
       </td>
     </tr>
+    <tr>
+      <td><code>VARIANT</code></td>
+      <td><code>Data type of semi-structured data.</code><br><br>
+          <code>Designed for storing any semi-structured data, including ARRAY, MAP, and scalar types. VARIANT can only store MAP types with keys of type STRING.</code><br><br>
+          <code>Note: Requires Flink 2.0+ and Spark 4.0+.</code>
+      </td>
+    </tr>
     <tr>
       <td><code>BLOB</code></td>
       <td><code>Data type of a binary large object.</code><br><br>