Add LastCommand to multicast packet

https://github.com/Hamlib/Hamlib/issues/695

README.multicast

@@ -77,6 +77,7 @@ Example JSON
   "Seq": 1,  
   "__comment_crc__": "32-bit CRC of entire JSON record replacing the CRC value with 0x00000000",
   "ErrorMsg": "OK",
+  "LastCommand": "Last command executed",
   "CRC": "0x00000000"
 }
 
@@ -128,6 +129,7 @@ namespace HamlibMultiCast
         public string Version;
         public string Status;
         public UInt32 Seq;
+        public string LastCommand;
         public string CRC;
         public SpectrumClass Spectrum { get; set; }
         public string ErrorMsg;

bindings/csharp/multicast/multicast.cs

@@ -40,6 +40,7 @@ namespace HamlibMultiCast
         public string App;
         public string Version;
         public UInt32 Seq;
+        public string LastCommand;
         public string CRC;
         public SpectrumClass Spectrum { get; set; }
     }

bindings/csharp/multicast/test.json

@@ -47,6 +47,7 @@
   "Version": "20210520", 
   "__comment_seq__": "Seq is 1-up sequence number 32-bit -- wraps around to 1 from 2^32-1",
   "Seq": 1,  
+  "LastCommand": "set_freq VFOA 14074000",
   "__comment_crc__": "32-bit CRC of entire JSON record replacing the CRC value with 0x00000000",
   "CRC": "0x00000000"
 }