Payload Format Indicator should be int8, not byte

[wlisac]

The Payload Format Indicator should be int8, not byte.

https://docs.oasis-open.org/mqtt/mqtt/v5.0/os/mqtt-v5.0-os.html#_Toc3901111

Here are a couple relevant places that would likely need to change.

mqtt-packet/constants.js

Line 108 in 1f1bb65

payloadFormatIndicator: 'byte',

mqtt-packet/types/index.d.ts

Line 72 in 1f1bb65

payloadFormatIndicator?: boolean,

[wlisac]

I just noticed that the Will Message's Payload Format Indicator already has a type annotation of number instead of boolean.

mqtt-packet/types/index.d.ts

Line 43 in 1f1bb65

payloadFormatIndicator?: number,

I think the publish packet using boolean instead of number is more of a semantic issue than an encoding issue (since the current possible values are only 0 or 1).

I'm happy to provide more information as needed.

Thanks,
Will