the docs are not quite up-to-date and generates warnings

bash-3.2$ make docs 
cmake ./ -B ./build -G "Ninja Multi-Config" -DCMAKE_BUILD_TYPE:STRING=Debug -DFEATURE_DOCS:BOOL=ON -DFEATURE_TESTS:BOOL=OFF
-- vcpkg is already installed at /Users/clausklein/vcpkg.
-- Running vcpkg install
Detecting compiler hash for triplet x64-osx...
The following packages will be built and installed:
    fmt[core]:x64-osx -> 8.1.1#1 -- /Users/clausklein/vcpkg/buildtrees/versioning_/versions/fmt/602d9743b7957c9e82a06d0e81d58637c6df5222
  * vcpkg-cmake[core]:x64-osx -> 2022-01-19 -- /Users/clausklein/vcpkg/buildtrees/versioning_/versions/vcpkg-cmake/b7c050fe60f91dcedef6d87a3f87584151bf8aee
  * vcpkg-cmake-config[core]:x64-osx -> 2022-02-06 -- /Users/clausklein/vcpkg/buildtrees/versioning_/versions/vcpkg-cmake-config/24dc7dfc704406e9f745f033643dc25f56e4ca18
Additional packages (*) will be modified to complete this operation.
Restored 3 packages from /Users/clausklein/.cache/vcpkg/archives in 31.4 ms. Use --debug to see more details.
Starting package 1/3: vcpkg-cmake-config:x64-osx
Installing package vcpkg-cmake-config[core]:x64-osx...
Elapsed time for package vcpkg-cmake-config:x64-osx: 1.857 ms
Starting package 2/3: vcpkg-cmake:x64-osx
Installing package vcpkg-cmake[core]:x64-osx...
Elapsed time for package vcpkg-cmake:x64-osx: 3.244 ms
Starting package 3/3: fmt:x64-osx
Installing package fmt[core]:x64-osx...
Elapsed time for package fmt:x64-osx: 9.997 ms

Total elapsed time: 1.783 s

The package fmt provides CMake targets:

    find_package(fmt CONFIG REQUIRED)
    target_link_libraries(main PRIVATE fmt::fmt)

    # Or use the header-only version
    find_package(fmt CONFIG REQUIRED)
    target_link_libraries(main PRIVATE fmt::fmt-header-only)

-- Running vcpkg install - done
-- The CXX compiler identification is AppleClang 13.1.6.13160021
-- The C compiler identification is AppleClang 13.1.6.13160021
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/c++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/cc - skipped
-- Detecting C compile features
-- Detecting C compile features - done
-- The default CMAKE_CXX_STANDARD used by external targets and tools is not set yet. Using the latest supported C++ standard that is 20
-- The default CMAKE_C_STANDARD used by external targets and tools is not set yet. Using the latest supported C standard that is 17
-- /usr/local/bin/ccache found and enabled
-- Found Doxygen: /usr/local/bin/doxygen (found version "1.9.3") found components: doxygen dot 
-- Adding `doxygen-docs` target that builds the documentation.
-- Configuring done
-- Generating done
-- Build files have been written to: /Users/clausklein/Workspace/cpp/cpp_cmake_project/build
cmake --build ./build --target doxygen-docs --config Debug
[1/1] Generating documentation - entry file: /Users/clausklein/Workspace/cpp/cpp_cmake_project/build/html/index.html
/Users/clausklein/Workspace/cpp/cpp_cmake_project/docs/building.md:79: warning: Invalid list item found
/Users/clausklein/Workspace/cpp/cpp_cmake_project/docs/dependencies.md:14: warning: unable to resolve reference to 'docker-instructions' for \ref command
/Users/clausklein/Workspace/cpp/cpp_cmake_project/docs/dependencies.md:52: warning: found </details> at different nesting level (12) than expected (9)
/Users/clausklein/Workspace/cpp/cpp_cmake_project/docs/dependencies.md:77: warning: found </details> at different nesting level (12) than expected (9)
/Users/clausklein/Workspace/cpp/cpp_cmake_project/docs/dependencies.md:121: warning: found </details> at different nesting level (9) than expected (6)
/Users/clausklein/Workspace/cpp/cpp_cmake_project/docs/dependencies.md:144: warning: found </details> at different nesting level (10) than expected (7)
/Users/clausklein/Workspace/cpp/cpp_cmake_project/docs/dependencies.md:163: warning: found </details> at different nesting level (10) than expected (7)
/Users/clausklein/Workspace/cpp/cpp_cmake_project/docs/dependencies.md:182: warning: found </details> at different nesting level (10) than expected (7)
/Users/clausklein/Workspace/cpp/cpp_cmake_project/docs/dependencies.md:216: warning: end of comment block while expecting command </details>
/Users/clausklein/Workspace/cpp/cpp_cmake_project/docs/dependencies.md:216: warning: end of comment block while expecting command </details>
/Users/clausklein/Workspace/cpp/cpp_cmake_project/docs/dependencies.md:216: warning: end of comment block while expecting command </details>
/Users/clausklein/Workspace/cpp/cpp_cmake_project/docs/dependencies.md:216: warning: end of comment block while expecting command </details>
/Users/clausklein/Workspace/cpp/cpp_cmake_project/docs/dependencies.md:216: warning: end of comment block while expecting command </details>
/Users/clausklein/Workspace/cpp/cpp_cmake_project/docs/dependencies.md:216: warning: end of comment block while expecting command </details>
/Users/clausklein/Workspace/cpp/cpp_cmake_project/docs/docker.md:12: warning: unable to resolve reference to 'dependencies' for \ref command
/Users/clausklein/Workspace/cpp/cpp_cmake_project/docs/docker.md:45: warning: unable to resolve reference to 'build' for \ref command
bash-3.2$ 

Run make docs and review the warnings reported for docs/building.md, docs/dependencies.md, and docs/docker.md. Start with the referenced lines and the surrounding documentation markup, then rebuild the documentation. Done means the listed invalid-list, nesting, and unresolved-reference warnings no longer appear.