Optional SCard Scope

[petrzjunior]

Windows SCard supports two different context scopes - USER and SYSTEM. The pcsclite implementation goes further with TERMINAL and GLOBAL, marked as unused though.

In case you need to lower the scope to comply with your machine's permissions, you are now able to specify a optional parameter in pcsclite constructor:

const pcsc = pcsclite({ scope: SCARD_SCOPE_USER });

From this line on, all pcsc contexts will be created with supplied scope.

Fixes #30