Add READMEs to every package #11297

Job	Run time
lint	2m 21s
test-race	1m 54s
test-bench	31s
compatibility-test (~1.22.0, ubuntu-latest, 386)	1m 7s
test-coverage	56s
compatibility-test (~1.22.0, ubuntu-latest, amd64)	27s
compatibility-test (~1.22.0, macos-latest, amd64)	1m 19s
compatibility-test (~1.22.0, windows-latest, 386)	3m 4s
compatibility-test (~1.22.0, windows-latest, amd64)	5m 51s
compatibility-test (~1.22.0, actuated-arm64-2cpu-8gb, arm64)	1m 43s
compatibility-test (~1.21.3, ubuntu-latest, 386)	25s
compatibility-test (~1.21.3, ubuntu-latest, amd64)	1m 5s
compatibility-test (~1.21.3, macos-latest, amd64)	1m 11s
compatibility-test (~1.21.3, windows-latest, 386)	3m 24s
compatibility-test (~1.21.3, windows-latest, amd64)	5m 24s
compatibility-test (~1.21.3, actuated-arm64-2cpu-8gb, arm64)	1m 42s
test-compatibility	1s
	32m 25s

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