Added custom build script to switch to pyproject.toml as single sourc… #166

Job	Run time
test (ubuntu-20.04, 3.6)	42s
test (ubuntu-20.04, 3.7)	50s
test (ubuntu-20.04, 3.8)	1m 0s
test (ubuntu-20.04, 3.9)	40s
test (ubuntu-20.04, 3.10)	1m 0s
test (ubuntu-20.04, 3.11)	42s
test (ubuntu-20.04, 3.12.0-rc.1)	1m 20s
test (ubuntu-20.04, pypy3.8)	1m 4s
test (ubuntu-20.04, pypy3.9)	1m 13s
test (ubuntu-20.04, pypy3.10)	1m 14s
test (macos-11, 3.6)	2m 16s
test (macos-11, 3.7)	2m 11s
test (macos-11, 3.8)	2m 9s
test (macos-11, 3.9)	2m 19s
test (macos-11, 3.10)	2m 46s
test (macos-11, 3.11)	2m 20s
test (macos-11, 3.12.0-rc.1)	4m 4s
test (macos-11, pypy3.8)	3m 13s
test (macos-11, pypy3.9)	2m 45s
test (macos-11, pypy3.10)	5m 3s
test (windows-2019, 3.6)	2m 41s
test (windows-2019, 3.7)	2m 38s
test (windows-2019, 3.8)	3m 31s
test (windows-2019, 3.9)	3m 37s
test (windows-2019, 3.10)	2m 57s
test (windows-2019, 3.11)	2m 59s
test (windows-2019, 3.12.0-rc.1)	6m 53s
test (windows-2019, pypy3.8)	4m 32s
test (windows-2019, pypy3.9)	2m 59s
test (windows-2019, pypy3.10)	6m 37s
builder_pypandoc	24s
builder_pypandoc_binary (macos-11)	1m 31s
builder_pypandoc_binary (windows-2019)	1m 23s
builder_pypandoc_binary (ubuntu-20.04)	1m 19s
publisher_latest	0s
publisher_release	0s
	1h 22m 52s

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