Add `TreeStyle` to PSTree #90

Job	Run time
build	1m 57s
test (PS-5.1, 5.1, windows-latest)	2m 0s
test (PS-7_Windows, 7, windows-latest)	1m 41s
test (PS-7_Linux, 7, ubuntu-latest)	29s
publish	0s
	6m 7s

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