Change KeywordSet to use Set().has(item.toLowerCase())

src/keyword-set.js

@@ -1,25 +1,16 @@
-import { strEquals } from "./string-utils.js"
-
 /**
  * @description A Set-like construct to search CSS keywords in a case-insensitive way
  */
 export class KeywordSet {
 
 	/** @param {string[]} items */
 	constructor(items) {
-		/** @type {string[]} */
-		this.set = items
+		/** @type {Set<string>} */
+		this.set = new Set(items)
 	}
 
 	/** @param {string} item */
 	has(item) {
-		let len = this.set.length
-
-		for (let index = 0; index < len; index++) {
-			if (strEquals(this.set[index], item)) {
-				return true
-			}
-		}
-		return false
+		return this.set.has(item.toLowerCase())
 	}
 }