doc(dijkstra): explain why we use an ArrayList

be-graphes-algos/src/main/java/org/insa/graphs/algorithm/shortestpath/DijkstraAlgorithm.java

@@ -36,6 +36,8 @@ public class DijkstraAlgorithm extends ShortestPathAlgorithm {
 
         // Init Dijkstra
         for (Node node : graph.getNodes()) {
+            // Luckily they are ordered by id.
+            // ArrayList.set only works if the value is already initialized (because why Java?)
             labels.add(new Label(node));
         }