Add initial pyproject.toml #748

Job	Run time
mypy	19s
build_python_27 (ubuntu-20.04, yes)	2m 48s
build_python_27 (ubuntu-20.04, no)	2m 43s
build_python_27 (windows-latest, yes)	4m 44s
build_python_27 (windows-latest, no)	4m 40s
test_c_linux (0, x64)	1m 16s
test_c_linux (0, x32)	1m 31s
test_c_linux (1, x64)	1m 49s
test_c_linux (1, x32)	1m 48s
test_c_windows (x64)	1m 34s
test_c_windows (win32)	1m 48s
build (3.5, yes, ubuntu-20.04)	2m 50s
build (3.5, no, ubuntu-20.04)	2m 47s
build (3.6, yes, ubuntu-20.04)	2m 43s
build (3.6, no, ubuntu-20.04)	2m 45s
build (3.7, yes, ubuntu-20.04)	2m 48s
build (3.7, no, ubuntu-20.04)	2m 42s
build (3.8, yes, ubuntu-20.04)	2m 33s
build (3.8, no, ubuntu-20.04)	2m 27s
build (3.9, yes, ubuntu-20.04)	3m 0s
build (3.9, no, ubuntu-20.04)	2m 27s
build (3.10, yes, ubuntu-20.04)	2m 58s
build (3.10, no, ubuntu-20.04)	2m 28s
build (3.11, yes, ubuntu-20.04)	2m 33s
build (3.11, no, ubuntu-20.04)	2m 40s
build (3.12-dev, yes, ubuntu-20.04)	3m 6s
build (3.12-dev, no, ubuntu-20.04)	2m 40s
build (3.11, yes, macos-12)	3m 15s
build (3.11, no, windows-latest)	5m 23s
build (3.11, yes, windows-latest)	5m 30s
build (3.12-dev, no, windows-latest)	6m 15s
build (3.12-dev, yes, windows-latest)	6m 28s
build (pypy2.7, no, ubuntu-latest)	2m 0s
build (pypy3.8, no, ubuntu-latest)	2m 3s
	1h 39m 21s

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