Update decimal dtypes related docs entries (#10072)

This PR adds `Decimal128Dtype` to the list of supported dtypes in docs.

Authors:
  - GALI PREM SAGAR (https://github.com/galipremsagar)

Approvers:
  - Vukasin Milovanovic (https://github.com/vuule)

URL: #10072

docs/cudf/source/basics/basics.rst

@@ -37,7 +37,8 @@ The following table lists all of cudf types. For methods requiring dtype argumen
     | Boolean                |                  | np.bool_                                                                            | ``'bool'``                                  |
     +------------------------+------------------+-------------------------------------------------------------------------------------+---------------------------------------------+
     | Decimal                | Decimal32Dtype,  | (none)                                                                              | (none)                                      |
-    |                        | Decimal64Dtype   |                                                                                     |                                             |
+    |                        | Decimal64Dtype,  |                                                                                     |                                             |
+    |                        | Decimal128Dtype  |                                                                                     |                                             |
     +------------------------+------------------+-------------------------------------------------------------------------------------+---------------------------------------------+
 
 **Note: All dtypes above are Nullable**

docs/cudf/source/basics/io-supported-types.rst

@@ -62,6 +62,8 @@ The following table lists are compatible cudf types for each supported IO format
     +-----------------------+--------+--------+--------+--------+---------+--------+--------+--------+--------+---------+---------+--------+--------+---------+---------+
     | decimal64             | ✅     | ✅     | ✅     | ✅     | ❌      | ❌     | ✅     | ✅     | ❌     | ❌      | ❌      | ❌     | ❌     | ❌      | ❌      |
     +-----------------------+--------+--------+--------+--------+---------+--------+--------+--------+--------+---------+---------+--------+--------+---------+---------+
+    | decimal128            | ✅     | ✅     | ✅     | ✅     | ❌      | ❌     | ✅     | ✅     | ❌     | ❌      | ❌      | ❌     | ❌     | ❌      | ❌      |
+    +-----------------------+--------+--------+--------+--------+---------+--------+--------+--------+--------+---------+---------+--------+--------+---------+---------+
 
 **Notes:**