Add DisjointSet and ForestDisjointSet documentation

Signed-off-by: Graham <gpe@openrs2.dev>

util/src/main/java/dev/openrs2/util/collect/DisjointSet.kt

@@ -1,5 +1,10 @@
 package dev.openrs2.util.collect
 
+/**
+ * A data structure containing a set of elements partitioned into a number of
+ * non-overlapping subsets. New elements belong to singleton subsets. The
+ * [union] function combines two subsets together into a single larger subset.
+ */
 interface DisjointSet<T> : Iterable<DisjointSet.Partition<T>> {
     interface Partition<T> : Iterable<T>
 

util/src/main/java/dev/openrs2/util/collect/ForestDisjointSet.kt

@@ -2,6 +2,11 @@ package dev.openrs2.util.collect
 
 import java.util.ArrayDeque
 
+/**
+ * A [DisjointSet] implementation backed by a disjoint-set forest, as described
+ * in chapter 21.3 of the third edition of CLRS. It uses path compression and
+ * union by rank.
+ */
 class ForestDisjointSet<T> : DisjointSet<T> {
     private class Node<T>(val value: T) : DisjointSet.Partition<T> {
         val children = mutableListOf<Node<T>>()