For non-Grav sites I have made in the past I have created an add to address book feature. For example on http://beautybydanny.com a link to http://beautybydanny.com/add-to-address-book/ goes to a VCF file whose headers are set accordingly (e.g., text/vcard).
In Grav, I’m not certain how to proceed. I tried dragging the VCF file into the Page Media area, but an error occurs: unsupported filetype. I’m okay with manually arranging it, but I don’t know the Grav-approved way to do this. Can someone please point me in the right direction?