feat: add CandidateWindow class to encapsulate interval and score

src/main/java/de/th_luebeck/ws25/CandidateWindow.java

@@ -0,0 +1,11 @@
+package de.th_luebeck.ws25;
+
+public class CandidateWindow {
+    Interval interval;
+    double score;
+
+    CandidateWindow(Interval interval, double score) {
+        this.interval = interval;
+        this.score = score;
+    }
+}