Tests

Add example for initializing a PCG RNG #619

Job	Run time
test-ios	42s
Check doc	1m 7s
test (ubuntu-latest, x86_64-unknown-linux-gnu, stable)	1m 2s
test (macos-latest, x86_64-apple-darwin, stable)	1m 30s
test-miri	3m 2s
test-no-std	11s
test (windows-latest, x86_64-pc-windows-gnu, stable)	2m 4s
test-cross (ubuntu-latest, powerpc-unknown-linux-gnu, stable)	2m 0s
test (windows-latest, x86_64-pc-windows-msvc, beta)	2m 0s
test (ubuntu-latest, x86_64-unknown-linux-gnu, MSRV, 1.60.0)	5m 2s
test (ubuntu-latest, sudo apt-get update ; sudo apt install gcc-multilib, i686-unknown-linux-gnu,...	1m 43s
test (ubuntu-latest, x86_64-unknown-linux-gnu, nightly, minimal_versions)	1m 27s
	21m 50s

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