Implemented Callback sample (#87) #210

Job	Run time
Code formatting	10s
Exercise Python examples on ubuntu-latest	2m 0s
Check Ruby Samples ubuntu-latest	1m 22s
Exercise Python examples on macos-latest	6m 56s
Check Ruby Samples macos-latest	2m 35s
Build Windows fetch	3m 3s
Build ubuntu-20.04 gcc os	1m 0s
Build Windows vcpkg	7m 28s
Build ubuntu-20.04 gcc fetch	1m 39s
Build ubuntu-20.04 gcc vcpkg	4m 3s
Build ubuntu-20.04 clang os	57s
Build ubuntu-20.04 clang fetch	2m 10s
Build ubuntu-20.04 clang vcpkg	4m 47s
Build macos-latest gcc os	2m 22s
Build macos-latest gcc fetch	2m 28s
Build macos-latest gcc vcpkg	2m 41s
Build macos-latest clang os	2m 45s
Build macos-latest clang fetch	2m 1s
Build macos-latest clang vcpkg	2m 20s
	52m 47s

Provide feedback