fdt sketch

[Yaron Illouz]

Hi

I don’t find fdt sketch in the https://github.com/apache/datasketches-cpp code 
as describe in 
https://datasketches.apache.org/docs/Frequency/FrequentDistinctTuplesSketch.html
I believe it is implemented because I can see example in the description
//Construct the sketch
FdtSketch sketch = new FdtSketch(0.01, 0.05);