added notice.

hbasm/src/lib.rs

@@ -69,6 +69,8 @@ impl Assembler {
         // - It was a good idea to add some equivalent to `ud2` anyways
         // - Its zeroes
         // - What if you somehow reached that code, it will appropriately bail :)
+        //
+        // Why 12 bytes? That's the size of largest instruction parameter part.
         self.buf.extend([0; 12]);
     }
 }