Update compile instructions
Simply copying the build instructions might lead to confusing errors:
CMake Error at ActionMan/CMakeLists.txt:8 (ki18n_wrap_ui):
Unknown CMake command "ki18n_wrap_ui".
CMake Warning (dev) in CMakeLists.txt:
No cmake_minimum_required command is present. A line of code such as
cmake_minimum_required(VERSION 3.16)