update cmake to 3.20

Author: finger563

CMakeLists.txt

@@ -1,6 +1,6 @@
 # The following lines of boilerplate have to be in your project's CMakeLists
 # in this exact order for cmake to work correctly
-cmake_minimum_required(VERSION 3.5)
+cmake_minimum_required(VERSION 3.20)
 
 include($ENV{IDF_PATH}/tools/cmake/project.cmake)