DOC-2844 added code sample for HyperLogLog (#282)

* DOC-2844 added code sample for HyperLogLog

* DOC-2844 use hashtags to fix cross-slot errors

Author: andy-stark-redis

tests/Doc/Hll_tutorial.cs

@@ -0,0 +1,58 @@
+// EXAMPLE: hll_tutorial
+// HIDE_START
+
+using NRedisStack.Tests;
+using StackExchange.Redis;
+
+// HIDE_END
+
+// REMOVE_START
+namespace Doc;
+[Collection("DocsTests")]
+// REMOVE_END
+
+// HIDE_START
+public class Hll_tutorial
+{
+
+    [SkipIfRedis(Is.OSSCluster)]
+    public void run()
+    {
+        var muxer = ConnectionMultiplexer.Connect("localhost:6379");
+        var db = muxer.GetDatabase();
+        //REMOVE_START
+        // Clear any keys here before using them in tests.
+        db.KeyDelete(new RedisKey[] { "{bikes}", "commuter_{bikes}", "all_{bikes}" });
+        //REMOVE_END
+        // HIDE_END
+
+
+        // STEP_START pfadd
+        bool res1 = db.HyperLogLogAdd("{bikes}", new RedisValue[] { "Hyperion", "Deimos", "Phoebe", "Quaoar" });
+        Console.WriteLine(res1);    // >>> True
+
+        long res2 = db.HyperLogLogLength("{bikes}");
+        Console.WriteLine(res2);    // >>> 4
+
+        bool res3 = db.HyperLogLogAdd("commuter_{bikes}", new RedisValue[] { "Salacia", "Mimas", "Quaoar" });
+        Console.WriteLine(res3);    // >>> True
+
+        db.HyperLogLogMerge("all_{bikes}", "{bikes}", "commuter_{bikes}");
+        long res4 = db.HyperLogLogLength("all_{bikes}");
+        Console.WriteLine(res4);    // >>> 6
+        // STEP_END
+
+        // Tests for 'pfadd' step.
+        // REMOVE_START
+        Assert.True(res1);
+        Assert.Equal(4, res2);
+        Assert.True(res3);
+        Assert.Equal(6, res4);
+        // REMOVE_END
+
+
+        // HIDE_START
+    }
+}
+// HIDE_END
+