appveyor.yml: Copy the README file in the .zip artifact.
appveyor.yml: Copy the README file in the .zip artifact.

Signed-off-by: Alexandra Trifan <951af57c14d42c73475635752bd213fd996792b2@analog.com>

analogdevicesinc/libiio,analogdevicesinc/libiio,analogdevicesinc/libiio,analogdevicesinc/libiio