support for non-standard option

[ev3nvy]

I am trying to connect to a server which has a custom SASL mechanism. I have no control over the server, and the SASL mechanism they use does not adhere to the xmpp specification.

According to formatting rule number 2 of the xmpp 6120 specification:

6.3.5. Data Formatting

Any XML character data contained within the XML elements MUST be
encoded using base 64, where the encoding adheres to the
definition in Section 4 of [BASE64] and where the padding bits
are set to zero.

SASL mechanism must have it's content b64 encoded, but the server I am connecting to doesn't do that. Instead, there is an xml tag in between which there are auth tokens. Example:

<auth xmlns="urn:ietf:params:xml:ns:xmpp-sasl" mechanism="X-TEST"><test>...</test></auth>

Since this goes against the standard, I wanted to ask first before making a pr. Something like parseSaslBody: boolean (default: true) is what I had in mind for a pr.
If this option were true the behavior is unchanged from how it is now.
If it's false, the string from response() would not be base64 encoded, neither would the text be escaped to character entities.

If you are against it, my best bet is making my own stripped down xmpp client based on this project - would that be ok?