sort combat zones

EDPlayerJournal/CombatZones.cs

@@ -38,4 +38,23 @@ public class CombatZones {
     /// Very high difficulty, so far AX combat zone only
     /// </summary>
     public static readonly string DifficultyVeryHigh = "Very High";
+
+    /// <summary>
+    /// Returns the given combat zone difficulty as an integer, so it can be sorted.
+    /// 0 = lowest difficulty, 1 = medium and so forth.
+    /// </summary>
+    public static int? DifficultyRank(string difficulty) {
+        Dictionary<string, int> ranks = new() {
+            { DifficultyLow, 0 },
+            { DifficultyMedium, 1 },
+            { DifficultyHigh, 2 },
+            { DifficultyVeryHigh, 3 }
+        };
+
+        if (ranks.TryGetValue(difficulty, out int rank)) {
+            return rank;
+        }
+
+        return null;
+    }
 }