Change IndexOf to string indexer

ValveKeyValue/ValveKeyValue.Test/Test Data/apisurface.txt

@@ -302,9 +302,9 @@ public sealed class ValveKeyValue.StringTable
     public bool Equals(object obj);
     protected void Finalize();
     public string get_Item(int index);
+    public int get_Item(string value);
     public int GetHashCode();
     public Type GetType();
-    public int IndexOf(string value);
     protected object MemberwiseClone();
     public void PrepareForSerialization();
     public string ToString();

ValveKeyValue/ValveKeyValue/Serialization/KeyValues1/KV1BinarySerializer.cs

@@ -90,7 +90,7 @@ void WriteKeyForNextValue(string name)
         {
             if (stringTable is not null)
             {
-                writer.Write(stringTable.IndexOf(name));
+                writer.Write(stringTable[name]);
             }
             else
             {

ValveKeyValue/ValveKeyValue/StringTable.cs

@@ -28,14 +28,17 @@ public string this[int index]
             }
         }
 
-        public int IndexOf(string value)
+        public int this[string value]
         {
-            if (reverse is null)
+            get
             {
-                throw new InvalidOperationException("String table has not been prepared for serialization.");
-            }
+                if (reverse is null)
+                {
+                    throw new InvalidOperationException("String table has not been prepared for serialization.");
+                }
 
-            return reverse[value];
+                return reverse[value];
+            }
         }
 
         public void PrepareForSerialization()