Move artworks folder to 'doc' directory #305

Job	Run time
CMake Build & Test (ubuntu-latest, Release, g++)	46s
CMake Build & Test (ubuntu-latest, Release, clang++)	51s
CMake Build & Test (ubuntu-latest, Debug, g++)	46s
CMake Build & Test (ubuntu-latest, Debug, clang++)	42s
CMake Build & Test (ubuntu-20.04, Release, g++)	54s
CMake Build & Test (ubuntu-20.04, Release, clang++)	57s
CMake Build & Test (ubuntu-20.04, Debug, g++)	42s
CMake Build & Test (ubuntu-20.04, Debug, clang++)	44s
CMake Build & Test (windows-latest, Release, cl)	1m 55s
CMake Build & Test (windows-latest, Debug, cl)	1m 41s
CMake Build & Test (windows-2019, Release, cl)	1m 38s
CMake Build & Test (windows-2019, Debug, cl)	1m 46s
CMake Build & Test (macos-11, Release, g++)	4m 32s
CMake Build & Test (macos-11, Release, clang++)	1m 30s
CMake Build & Test (macos-11, Debug, g++)	1m 28s
CMake Build & Test (macos-11, Debug, clang++)	1m 48s
CMake Build & Test (macos-13, Release, g++)	57s
CMake Build & Test (macos-13, Release, clang++)	57s
CMake Build & Test (macos-13, Debug, g++)	45s
CMake Build & Test (macos-13, Debug, clang++)	44s
	26m 3s

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