Refactored API, added kotlin extensions

eco-api/api-kotlin/build.gradle

@@ -0,0 +1,31 @@
+buildscript {
+    repositories {
+        mavenCentral()
+    }
+
+    dependencies {
+        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:1.6.0"
+    }
+}
+
+apply plugin: "kotlin"
+
+group 'com.willfp'
+version rootProject.version
+
+dependencies {
+    compileOnly 'org.jetbrains.kotlin:kotlin-stdlib:1.6.0'
+    compileOnly project(":eco-api:api-java")
+}
+
+compileKotlin {
+    kotlinOptions {
+        jvmTarget = "17"
+    }
+    targetCompatibility = JavaVersion.VERSION_17
+    sourceCompatibility = JavaVersion.VERSION_17
+}
+
+java {
+    withJavadocJar()
+}

eco-api/api-kotlin/src/main/kotlin/com/willfp/eco/util/kotlin/ListUtils.kt

@@ -0,0 +1,17 @@
+@file:JvmName("ListUtilsExtensions")
+
+package com.willfp.eco.util.kotlin
+
+import com.willfp.eco.util.ListUtils
+
+/**
+ * @see ListUtils.listToFrequencyMap
+ */
+fun <T> List<T>.toFrequencyMap(): Map<T, Int> =
+    ListUtils.listToFrequencyMap(this)
+
+/**
+ * @see ListUtils.containsIgnoreCase
+ */
+fun Iterable<String>.containsIgnoreCase(element: String): Boolean =
+    ListUtils.containsIgnoreCase(this, element)