macOS

Reorganize top-level doc files for better doc navigation #7876

Job	Run time
make (check, macos-14)	6m 8s
make (check, macos-14, --with-gcc=gcc-14)	7m 35s
make (check, macos-14, --with-jemalloc --with-opt-dir=$(brew --prefix jemalloc))	6m 44s
make (check, macos-14, --with-gmp)	5m 48s
make (test-all, --repeat-count=2, macos-14)	8m 26s
make (test-bundler-parallel, macos-14)	17m 13s
make (test-bundled-gems, macos-14)	8m 51s
make (check, macos-15)	5m 23s
make (check, macos-13)	12m 7s
macOS result	1s
	1h 18m 16s

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