Add helper method to get all learnable moves up to a specific level

PkmnLib.Static/Species/LearnableMoves.cs

@@ -34,6 +34,11 @@ public interface ILearnableMoves
     /// <returns>The moves the Pokémon can learn through leveling up.</returns>
     IReadOnlyList<StringKey> GetDistinctLevelMoves();
 
+    /// <summary>
+    /// Gets a list of all moves a Pokémon can learn up to a specific level.
+    /// </summary>
+    IReadOnlyList<StringKey> GetLearnableMovesUpToLevel(LevelInt level);
+    
     /// <summary>
     /// Gets all moves a Pokémon can learn by breeding.
     /// </summary>
@@ -81,6 +86,17 @@ public class LearnableMovesImpl : ILearnableMoves
         return _distinctLevelMoves.ToList();
     }
 
+    /// <inheritdoc />
+    public IReadOnlyList<StringKey> GetLearnableMovesUpToLevel(LevelInt level)
+    {
+        var moves = new HashSet<StringKey>();
+        foreach (var kvp in _learnedByLevel.TakeWhile(kvp => kvp.Key <= level))
+        {
+            moves.UnionWith(kvp.Value);
+        }
+        return moves.ToList();
+    }
+
     /// <inheritdoc />
     public IReadOnlyList<StringKey> GetEggMoves() => _eggMoves;
 }