Signing the .dmg for MacOS

Sometimes when first-time users download the dmg file for MacOS, they have to go through a long process of allowing their Mac to run the application, would be great if we just signed it.

**Describe the solution you'd like**
We could try and sign the .dmg file for free if we register it with the [Fee Waiver Program](https://developer.apple.com/support/fee-waiver/) at apple.