docs(fix): example code uses private state var instead of internal - #44

[brillaintlcd]

Updated the docs to use internal state variable instead of private as this is not supported and will throw a build error.

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[marcprux]

Thanks!

[marcprux]

FYI, we might eventually have support for private state (if skiptools/skipstone#282 get tested more and lands). But for the time being we should have the docs represent what we support right now.