Make header library available for CMake's FetchContent

[cprieto]

Now the header library is available using FetchContent, for example:

cmake_minimum_required(VERSION 3.28)
project(blah LANGUAGES C)

set(CMAKE_C_STANDARD 11)
set(CMAKE_C_STANDARD_REQUIRED YES)

Include(FetchContent)
FetchContent_Declare(
  CloveUnit
  GIT_REPOSITORY https://github.com/fdefelici/clove-unit.git
  GIT_TAG v2.4.5
)
FetchContent_MakeAvailable(CloveUnit)

add_executable(all_tests all_tests.c test_suite1.c)
target_link_libraries(all_tests PRIVATE CloveUnit)

[fdefelici]

Summary of the improvements made:

• library naming: clove-unit
• set minimum compiler to: c_std_11
• avoid to import development targets and test specific configuration
• update Readme with CMAke dependency management examples