Extend documentation with information on how to manage a `ControlPlaneMachineSet` #144

Job	Run time
editorconfig	5s
linting (lint_jsonnet)	6s
golden (defaults)	18s
linting (lint_yaml)	6s
golden (gcp)	17s
test (defaults)	20s
linting (lint_adoc)	7s
golden (maxpods)	18s
test (gcp)	17s
golden (pidslimit)	17s
test (maxpods)	17s
golden (machineconfig)	19s
test (pidslimit)	18s
golden (remove-machineconfigpool)	18s
test (machineconfig)	21s
test (remove-machineconfigpool)	18s
	4m 2s

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