Wrong handling of Binary comments (BinaryMessage.ts)

[nns2009]

In: https://github.com/tonwhales/ton/blob/master/src/messages/BinaryMessage.ts
binary comments are not handled according to guidelines: https://ton.org/docs/#/howto/smart-contract-guidelines

If op is zero, then the message is a "simple transfer message with comment". The comment is contained in the remainder of the message body (without any query_id field, i.e., starting from the fifth byte). If it does not begin with the byte 0xff, the comment is a text one; ... On the other hand, if the comment begins with the byte 0xff, the remainder is a "binary comment"

In other words, need bytes 0x00000000FF before writing buffer

Suggested fix:

writeTo(cell: Cell) {
    cell.bits.writeUint(0, 32);
    cell.bits.writeUint(0xFF, 8);
    cell.bits.writeBuffer(this.payload);
}

Another issue is handling big binary comments which don't into one cell.
The case of big messages is handled in for text comments in CommentMessage.ts, but not for binary comments.

[ex3ndr]

Hello! Thank you for your contribution, but in our library BinaryMessage does not a "binary comment" from original whitepaper, but a simple wrapper on top of a buffer and simply a convenient way to write a buffer using messages.

Also we haven't seen binary comments in practice. We are looking to improve this part in next releases.