make: relax cmake version for CI

CMakeLists.txt

-cmake_minimum_required(VERSION 3.13)
+cmake_minimum_required(VERSION 3.10)
 
 project(flow-code LANGUAGES CXX)
 
 add_subdirectory(imageLib)
 
-
 add_executable(color_flow color_flow.cpp flowIO.cpp colorcode.cpp)
 target_include_directories(color_flow PRIVATE imageLib)
 target_link_libraries(color_flow PRIVATE imageLib PUBLIC png z)