chore: add javadoc for CollectionUtils.chunked and set initialCapacity

common/src/main/java/com/github/twitch4j/common/util/CollectionUtils.java

@@ -1,19 +1,26 @@
 package com.github.twitch4j.common.util;
 
 import java.util.ArrayList;
-import java.util.Arrays;
 import java.util.Iterator;
 import java.util.List;
 
 public class CollectionUtils {
 
+    /**
+     * Assigns elements of the given iterable to chunks not exceeding the desired size
+     *
+     * @param iterable the source of elements to be assigned to a chunk
+     * @param size the maximum size of each chunk
+     * @return a list of the chunks, or an empty list if the iterable yielded no elements
+     * @throws NullPointerException if the passed iterable is null
+     */
     public static <T> List<List<T>> chunked(Iterable<T> iterable, int size) {
         List<List<T>> chunks = new ArrayList<>();
         List<T> chunk = null;
         Iterator<T> it = iterable.iterator();
         for (int i = 0; it.hasNext(); i++) {
             if (i % size == 0) {
-                chunk = new ArrayList<>();
+                chunk = new ArrayList<>(size);
                 chunks.add(chunk);
             }