DOC-4323 added INCR command example (#3141)

Co-authored-by: ofekshenawa <104765379+ofekshenawa@users.noreply.github.com>

doctests/cmds_string_test.go

@@ -0,0 +1,57 @@
+// EXAMPLE: cmds_string
+// HIDE_START
+package example_commands_test
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/redis/go-redis/v9"
+)
+
+// HIDE_END
+
+func ExampleClient_cmd_incr() {
+	ctx := context.Background()
+
+	rdb := redis.NewClient(&redis.Options{
+		Addr:     "localhost:6379",
+		Password: "", // no password docs
+		DB:       0,  // use default DB
+	})
+
+	// REMOVE_START
+	rdb.Del(ctx, "mykey")
+	// REMOVE_END
+
+	// STEP_START incr
+	incrResult1, err := rdb.Set(ctx, "mykey", "10", 0).Result()
+
+	if err != nil {
+		panic(err)
+	}
+
+	fmt.Println(incrResult1) // >>> OK
+
+	incrResult2, err := rdb.Incr(ctx, "mykey").Result()
+
+	if err != nil {
+		panic(err)
+	}
+
+	fmt.Println(incrResult2) // >>> 11
+
+	incrResult3, err := rdb.Get(ctx, "mykey").Result()
+
+	if err != nil {
+		panic(err)
+	}
+
+	fmt.Println(incrResult3) // >>> 11
+	// STEP_END
+
+	// Output:
+	// OK
+	// 11
+	// 11
+}