Add tilt computation for design targets #235

Job	Run time
Tox test (py38)	3m 22s
Tox test (py39)	3m 10s
Tests on paywalled platforms (macos-13-xlarge, 3.12)	1m 25s
Tox test (py310)	3m 17s
Tests on other platforms (windows-2019, 3.10)	3m 49s
Tox test (py311)	3m 10s
Tests on other platforms (windows-2022, 3.11)	4m 21s
Tox test (py312-cover)	6m 31s
Tests on other platforms (windows-2022, 3.12)	3m 19s
Tests on other platforms (macos-12, 3.11)	3m 8s
Tests on other platforms (macos-13, 3.12)	4m 46s
Tox test (docs, graphviz)	1m 57s
Docker image	48s
PyPI packaging	0s
	43m 3s

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