Add typings for PlotAction #1242

Job	Run time
Python 3.7 on ubuntu-20.04 PyQt5 sdist	7m 1s
Python 3.7 on ubuntu-20.04 PyQt5 sdist	7m 1s
Python 3.10 on macos-latest PyQt5 wheel	13m 9s
Python 3.10 on macos-latest PyQt5 wheel	12m 40s
Python 3.8 on ubuntu-latest PySide6 sdist	7m 29s
Python 3.8 on ubuntu-latest PySide6 sdist	7m 29s
Python 3.9 on macos-latest PySide6 wheel	13m 25s
Python 3.9 on macos-latest PySide6 wheel	11m 54s
Python 3.7 on ubuntu-latest PyQt6 wheel	6m 29s
Python 3.7 on ubuntu-latest PyQt6 wheel	6m 29s
Python 3.10 on macos-latest PyQt6 wheel	13m 29s
Python 3.10 on macos-latest PyQt6 wheel	11m 9s
Python 3.9 on windows-latest No GUI wheel	6m 38s
Python 3.9 on windows-latest No GUI wheel	6m 38s
	2h 11m 0s

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