Setting MERGIN_AUTH hint for Windows users

[erpas]

When users log in to the service they would see the hint how to set up the env variable:

To set the MERGIN_AUTH variable run:
export MERGIN_AUTH="Bearer .eJwljUkK[....]UPrHSAHfiwwJYPoE"

This works nicely on GNU/Linux machines but would fail on Windows.
Would it be possible to also add a version of the hint for Windows users? For example:

On Windows:
SET MERGIN_AUTH=Bearer .eJwljUkK[....]UPrHSAHfiwwJYPoE

Please note there are no quotations.

[wonder-sk]

Fixed in #175