op-guide: add accessing Spark with Python or R

Via: pingcap/tidb-docker-compose#27, pingcap/docs#546

Author: lilin90

op-guide/docker-compose.md

@@ -151,4 +151,13 @@ scala> spark.sql("select count(*) from lineitem").show
 +--------+
 |   60175|
 +--------+
-```
+```
+
+你也可以通过 Python 或 R 来访问 Spark：
+
+```bash
+docker-compose exec tispark-master /opt/spark/bin/pyspark
+docker-compose exec tispark-master /opt/spark/bin/sparkR
+```
+
+更多关于 TiSpark 的信息，参见 [TiSpark 的详细文档](../tispark/tispark-quick-start-guide.md)。