Added keyvalue load actor config example (#1045)

Author: domwst

ydb/core/load_test/config_examples.cpp

@@ -25,6 +25,20 @@ TVector<TConfigTemplate> BuildExamples() {
         ColumnsCnt: 2
         RowsCnt: 1
     }
+})_"
+        },
+        TConfigTemplate{
+            .LoadName = "KeyValueLoad",
+            .Template = R"_(KeyValueLoad: {
+    TargetTabletId: xxx
+    DurationSeconds: 120
+    Workers {
+        KeyPrefix: "LoadTest_"
+        MaxInFlight: 128
+        Size: 1024
+        IsInline: false
+        LoopAtKeyCount: 0
+    }
 })_"
         },
         TConfigTemplate{