test

Revise Timeout.timeout docs and add a section about `ensure` #272

Job	Run time
ruby-versions / Generate Ruby versions	5s
build (2.7 / macos-latest)	34s
build (2.7 / ubuntu-latest)	25s
build (2.6 / ubuntu-latest)	25s
build (2.6 / macos-latest)	51s
build (3.0 / ubuntu-latest)	12s
build (3.0 / macos-latest)	19s
build (3.1 / macos-latest)	13s
build (3.2 / ubuntu-latest)	14s
build (3.1 / ubuntu-latest)	10s
build (3.3 / macos-latest)	15s
build (head / ubuntu-latest)	12s
build (3.2 / macos-latest)	17s
build (truffleruby-head / macos-latest)	31s
build (head / macos-latest)	18s
build (truffleruby / ubuntu-latest)	28s
build (3.3 / ubuntu-latest)	12s
build (3.4 / macos-latest)	15s
build (3.4 / ubuntu-latest)	10s
	6m 6s

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