Adjust CMake minimal version

[nlohmann]

• Use CMake 4.0.0 in the CI.
• Change the CMake version range for the project from

  cmake_minimum_required(VERSION 3.1...3.14)

  to

  cmake_minimum_required(VERSION 3.5...4.0)

• Adjust the ci_cmake_flags CI target to use the following CMake versions:
  • CMake 3.5 (the earliest supported)
  • CMake 3.31.6 (the latest 3.x release)
  • CMake 4.0.0 (the latest release)
• Adjust all test CMake files to use 3.5 as minimal versions
• Adjust documentation accordingly
• Off-topic: Added Microsoft Teams to list of customers

[coveralls]

coverage: 99.186%. remained the same
when pulling 255921c on cmake-min-version
into 3a57039 on develop.