refctor: replace indexOf with strict equality

lib/rules/sort-character-class-elements.ts

@@ -296,17 +296,17 @@
         ) {
             raw = `\\${raw}`
         }
-    } else if (raw.startsWith("^")) {
+    } else if (raw[0] === "^") {
         const parent = target.parent as CharacterClass
         const elements: (
             | UnicodeSetsCharacterClassElement
             | ClassRangesCharacterClassElement
         )[] = parent.elements
-        if (elements.indexOf(target) === 0) {
+        if (elements[0] === target) {
             raw = `\\${raw}`
         }
     }
-    if (target.raw.startsWith("-")) {
+    if (target.raw[0] === "-") {
         if (node.type === "Character" || node.type === "CharacterSet") {
             raw = `${raw}\\`
         }