✨ EnumerableSetLib indexOf

[Vectorized]

Description

Warm up.

Checklist

Ensure you completed all of the steps below before submitting your pull request:

• Ran forge fmt?
• Ran forge test?

Pull requests with an incomplete checklist will be thrown out.

[github-actions]

Gas Snapshot Comparison Report

Generated at commit : 5a16cf7, Compared to commit : 2718072

Contract Name	Test Name	Main Gas	PR Gas	Diff
EnumerableSetLibTest	testEnumerableAddressSetBasic()	248509	248487	-22
	testEnumerableAddressSetBasic2()	175327	175345	18
	testEnumerableAddressSetNoStorageCollision()	99016	98994	-22
	testEnumerableAddressSetUpdate()	200022	200087	65
	testEnumerableBytes32SetBasic()	271260	271238	-22
	testEnumerableUint8Set()	69240	69218	-22
	test__codesize()	19761	21371	1610