@extra-string/find-index (npm): Get index of first value that satisfies the test, like `Array.findIndex()`.
Keywords: extra|string|standard|utility|method|text|manipulation|function|merferry|find|index|at|compare-function|digits|hex-digits|infix|is-infix|is-prefix|is-suffix|left|letters|lowercase|map-function|prefix|replace-function|right|size|suffix|test-function