add R to TOCTree

docs/source/index.rst

@@ -37,6 +37,7 @@ To learn more about ADBC, see the `introductory blog post
    Go <https://pkg.go.dev/github.com/apache/arrow-adbc/go/adbc>
    Java <java/index>
    Python <python/index>
+   R <r/index>
 
 .. toctree::
    :maxdepth: 1

docs/source/r/index.rst

@@ -0,0 +1,30 @@
+.. 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.
+
+===
+R
+===
+
+-------------
+API Reference
+-------------
+
+- `adbcdrivermanager <adbcdrivermanager/index.html>`_
+- `adbcflightsql <adbcflightsql/index.html>`_
+- `adbcpostgresql <adbcpostgresql/index.html>`_
+- `adbcsnowflake <adbcsnowflake/index.html>`_
+- `adbcsqlite <adbcsqlite/index.html>`_