Update platform support docs to include macOS 10.14 Mojave

Puppet for OSX-10.14 will come with some limitations due to OSX-10.14 "Full Disk Access" restrictions. For now we have confirmed that managing users and groups using puppet is not working properly if `puppet executable` is not whitelisted in FDA. Other issues that we are not aware of might appear when using puppet without being whitelisted in FDA. You can find information about FDA here: https://macpaw.com/how-to/full-disk-access-mojave Whitelisting an app for FDA can be done in two official ways: Manual by the owner of the Macbook by clicking on the Apple icon > System Preferences > Go to Security & Privacy > Click on the privacy tab > Click Full Disk Access section in the side bar > Click on the “+” and add the path to the puppet executable: . Link: https://support.intego.com/hc/en-us/articles/360016683471-Enable-Full-Disk-Access-in-macOS-Mojave Automated using Privacy Preferences Control Profiles (PPCP) and a Mobile Device Management (MDM) Server.** I think we might need to document this steps and why is this needed. Let me know if you have any questions about this.