Use base64 padding when encoding in the notify kitten

Otherwise kitty warns about incomplete base64 data in its stderr

kittens/notify/main.go

@@ -25,7 +25,7 @@ const ESC_CODE_SUFFIX = "\x1b\\"
 const CHUNK_SIZE = 4096
 
 func b64encode(x string) string {
-	return base64.RawStdEncoding.EncodeToString(utils.UnsafeStringToBytes(x))
+	return base64.StdEncoding.EncodeToString(utils.UnsafeStringToBytes(x))
 }
 
 func check_id_valid(x string) bool {