Add build-system section for pyproject (oops), update changelog. #61

Job	Run time
build (3.8, sphinx)	1m 9s
build (3.9, sphinx)	1m 3s
build (3.10, sphinx)	1m 3s
build (3.11, sphinx)	1m 3s
build (3.12, sphinx)	1m 37s
build (3.7, "docutils<0.18" "jinja2<3.1")	1m 7s
build (3.12, sphinx https://github.com/numpy/numpydoc/archive/refs/heads/master.zip, -m "numpydoc")	50s
build (3.12, sphinx https://github.com/brechtm/rinohtype/archive/refs/heads/master.zip, -m "rinoh...	47s
build (3.12, sphinx test/some_cython_module, -m "cython")	49s
build (3.9, "sphinx<4" "jinja2<3.1" "sphinxcontrib-applehelp<1.0.8" "sphinxcontrib-devhelp<1.0.5"...	1m 5s
build (3.10, "sphinx<5" "sphinxcontrib-applehelp<1.0.8" "sphinxcontrib-devhelp<1.0.5" "sphinxcont...	1m 7s
build (3.12, "sphinx<6")	1m 15s
build (3.12, "sphinx<7")	1m 19s
	14m 14s

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