Add JSON serialization #138

Job	Run time
build (macos-latest, Debug, clang, clang++)	2m 3s
build (macos-latest, Release, clang, clang++)	1m 33s
build (ubuntu-latest, Debug, clang, clang++)	2m 49s
build (ubuntu-latest, Release, clang, clang++)	2m 33s
build (windows-latest, Release, clang, clang++)	2m 22s
build (windows-latest, Debug, clang, clang++)	1m 46s
	13m 6s

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