update message.proto

Add some comments so that I don't forget about these

License: MIT
Signed-off-by: David Dias <daviddias.p@gmail.com>

exchange/bitswap/message/pb/message.proto

@@ -5,21 +5,21 @@ message Message {
   message Wantlist {
 
     message Entry {
-      optional string block = 1; // the block key
-      optional int32 priority = 2; // the priority (normalized). default to 1
-      optional bool cancel = 3;  // whether this revokes an entry
+      optional string block = 1; 	// the block cid (cidV0 in bitswap 1.0.0, cidV1 in bitswap 1.1.0)
+      optional int32 priority = 2; 	// the priority (normalized). default to 1
+      optional bool cancel = 3;  	// whether this revokes an entry
     }
 
-    repeated Entry entries = 1; // a list of wantlist entries
-    optional bool full = 2;     // whether this is the full wantlist. default to false
+    repeated Entry entries = 1; 	// a list of wantlist entries
+    optional bool full = 2;     	// whether this is the full wantlist. default to false
   }
 
   message Block {
-	optional bytes prefix = 1;
-	optional bytes data = 2;
+    optional bytes prefix = 1;		// CID prefix (cid version, multicodec and multihash prefix (type + length)
+    optional bytes data = 2;
   }
 
   optional Wantlist wantlist = 1;
-  repeated bytes blocks = 2;
-  repeated Block payload = 3;
+  repeated bytes blocks = 2;		// used to send Blocks in bitswap 1.0.0
+  repeated Block payload = 3;		// used to send Blocks in bitswap 1.1.0
 }