fix: do not report types implementing `(Un)Marshaler` #91

Job	Run time
vuln / vuln	31s
lint / lint	10s
test / test (ubuntu-latest, oldstable)	40s
test / test (ubuntu-latest, stable)	49s
test / test (windows-latest, oldstable)	2m 16s
test / test (windows-latest, stable)	1m 51s
test / test (macos-latest, oldstable)	1m 5s
test / test (macos-latest, stable)	1m 9s
	8m 31s

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