Changes C64 ROM auto-download from commodore.ca to zimmers.net (#163)

Author: highbyte

src/libraries/Highbyte.DotNet6502.Systems.Commodore64/Config/C64SystemConfig.cs

@@ -75,13 +75,16 @@ public void SetRenderTargetType(Type renderTargetType)
         _isDirty = true;
     }
 
-    public static string DEFAULT_KERNAL_ROM_DOWNLOAD_BASE_URL = "https://www.commodore.ca/manuals/funet/cbm/firmware/computers/c64/";
+    // Note: Original download URL on commodore.ca no longer works, Cloudflare bot detection probably uses TLS fingerprinting and detects .NET httpclient as a bot.
+    //public static string DEFAULT_KERNAL_ROM_DOWNLOAD_BASE_URL = "https://www.commodore.ca/manuals/funet/cbm/firmware/computers/c64/";
+
+    public static string DEFAULT_KERNAL_ROM_DOWNLOAD_BASE_URL = "http://www.zimmers.net/anonftp/pub/cbm/firmware/computers/c64";
     public static string DEFAULT_KERNAL_ROM_DOWNLOAD_URL = $"{DEFAULT_KERNAL_ROM_DOWNLOAD_BASE_URL}/kernal.901227-03.bin";
     public static string DEFAULT_BASIC_ROM_DOWNLOAD_URL = $"{DEFAULT_KERNAL_ROM_DOWNLOAD_BASE_URL}/basic.901226-01.bin";
     public static string DEFAULT_CHARGEN_ROM_DOWNLOAD_URL = $"{DEFAULT_KERNAL_ROM_DOWNLOAD_BASE_URL}/characters.901225-01.bin";
 
     // TODO: Decide if ROM checksums should exist in C64SystemConfig, C64Config, or in C64
-    // ROM version info from: https://www.commodore.ca/manuals/funet/cbm/firmware/computers/c64/
+    // ROM version info from: http://www.zimmers.net/anonftp/pub/cbm/firmware/computers/c64/
     // Checksums calculated with SHA1
     public const string KERNAL_ROM_NAME = "kernal";
     public static Dictionary<string, string> DefaultKernalROMChecksums = new()