allow curseforge and modrinth as source

ModpackUpdater/InstallAction.cs

@@ -1,4 +1,5 @@
 using Newtonsoft.Json;
+using Newtonsoft.Json.Converters;
 using System.ComponentModel;
 
 namespace ModpackUpdater;
@@ -27,6 +28,7 @@ public class InstallAction
     public string SourceUrl { get; set; }
 
     [DefaultValue(SourceType.DirectLink)]
+    [JsonConverter(typeof(StringEnumConverter))]
     public SourceType SourceType { get; set; }
 
     [DefaultValue(null)]
@@ -42,6 +44,7 @@ public class InstallAction
     public string SourceTag { get; set; }
 
     [DefaultValue(Side.Both)]
+    [JsonConverter(typeof(StringEnumConverter))]
     public Side Side { get; set; } = Side.Both;
 
     [DefaultValue(false)]