Generalize isSymmetrical() to a list of arbitrary type

The only condition is that the list elements' type implements equals()
which is provided on `Any` level.

Author: rhaendel

src/main/kotlin/de/ronny_h/aoc/extensions/Symmetries.kt

@@ -1,6 +1,6 @@
 package de.ronny_h.aoc.extensions
 
-fun List<Int>.isSymmetrical(): Boolean {
+fun <T> List<T>.isSymmetrical(): Boolean {
     for (i in 0..<size / 2) {
         if (this[i] != this[lastIndex - i]) return false
     }

src/test/kotlin/de/ronny_h/aoc/extensions/SymmetriesTest.kt

@@ -13,7 +13,11 @@ class SymmetriesTest : StringSpec({
         listOf(1, 2, 3, 2, 1).isSymmetrical() shouldBe true
     }
 
-    "a asymmetrical list is not symmetrical" {
+    "a symmetrical list of Strings is symmetrical" {
+        listOf("a", "b", "c", "b", "a").isSymmetrical() shouldBe true
+    }
+
+    "an asymmetrical list is not symmetrical" {
         listOf(4, 2, 3, 2, 1).isSymmetrical() shouldBe false
     }
 })