Epidemiological metrics for netdiffuseR #174

Job	Run time
build-pkg	4m 59s
macOS-latest (devel) (valgrind:)	2m 57s
windows-latest (release) (valgrind:)	10m 24s
ubuntu-latest (release) (valgrind:)	5m 38s
ubuntu-latest (devel) (valgrind:)	11m 35s
ubuntu-latest (devel) (valgrind:true)	22m 10s
macOS-latest (release) (valgrind:)	8m 22s
	1h 6m 5s

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