[parser-packet-length] - Support multi-byte delimiter

[alferz]

It would be awesome if this parser could support a multiple byte delimiter. I have run into times where a protocol defines a 2-byte start sequence, such as 0xAA 0x43. In the current implementation I can use 0xAA but specifying an additional level of specificity would help cut down on possible errors. Could the 'delimiter' property accept a Buffer in addition to a number?

[bbeck13]

I've done this here #2709 I've also added support for multiple delimiters