Tests

Add notebook-link badge in the README #800

Job	Run time
build	2m 20s
Test (ubuntu, 3.13, latest, ipympl*.whl)	2m 7s
Test (ubuntu, 3.14, latest, ipympl*.whl)	2m 8s
Test (macos, 3.9, latest, ipympl*.whl)	1m 34s
Test (macos, 3.14, latest, ipympl*.whl)	1m 34s
Test (macos, 3.13, latest, ipympl*.whl)	1m 46s
Test (ubuntu, 3.9, 3.5, ipympl*.whl)	2m 31s
Test (ubuntu, 3.9, latest, ipympl*.whl)	2m 36s
Test (ubuntu, 3.11, latest, ipympl*.tar.gz)	3m 14s
	19m 50s

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