feat: add IsCaseInsensitive

[zoncoen]

Code Metrics Report

	main (f19d6a5)	#55 (27be99f)	+/-
Coverage	93.7%	93.7%	-0.0%
Code to Test Ratio	1:1.7	1:1.7	+0.0

Details

  |                    | main (f19d6a5) | #55 (27be99f) |  +/-  |
  |--------------------|----------------|---------------|-------|
- | Coverage           |          93.7% |         93.7% | -0.0% |
  |   Files            |             12 |            13 |    +1 |
  |   Lines            |            542 |           555 |   +13 |
+ |   Covered          |            508 |           520 |   +12 |
+ | Code to Test Ratio |          1:1.7 |         1:1.7 |  +0.0 |
  |   Code             |            772 |           793 |   +21 |
+ |   Test             |           1341 |          1380 |   +39 |

Code coverage of files in pull request scope (97.1% → 96.5%)

Files	Coverage	+/-
context.go	87.5%	+87.5%
key.go	97.2%	+0.1%

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Reported by octocov