Add doctest example for Op in cats core #3110

Job	Run time
Validate Steward Config (ubuntu-22.04, temurin@11)	20s
Generate Site (ubuntu-22.04, temurin@17)	3m 19s
Scalafix (ubuntu-22.04, temurin@8)	52s
Test (ubuntu-22.04, 2.12, temurin@8, catsNative)	12m 13s
Test (ubuntu-22.04, 2.12, temurin@8, catsJVM)	7m 23s
Test (ubuntu-22.04, 2.13, graalvm@21, catsJVM)	4m 27s
Test (ubuntu-22.04, 2.12, temurin@8, catsJS)	7m 40s
Test (ubuntu-22.04, 3, temurin@8, catsJS)	9m 17s
Test (ubuntu-22.04, 2.13, temurin@8, catsJS)	7m 56s
Test (ubuntu-22.04, 2.13, temurin@17, catsJVM)	4m 48s
Test (ubuntu-22.04, 2.13, temurin@8, catsNative)	12m 15s
Test (ubuntu-22.04, 3, temurin@8, catsJVM)	9m 12s
Submit Dependencies	0s
Test (ubuntu-22.04, 2.13, temurin@8, catsJVM)	7m 27s
Test (ubuntu-22.04, 3, temurin@8, catsNative)	13m 19s
Publish Artifacts	-1s
	1h 40m 27s

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