Sign MacOS installer

[Hal-9k1]

Right now, macOS users see an intimidating looking warning about unsigned apps when trying to install the app from a DMG. Then, in order to complete the installation, they have to go in their settings and allow uncharted apps to run, which would sound really shady if we put that in our installation instructions. Though it won’t be a short process, this is a problem we can fix. As far as I understand right now the steps are:

1. Obtain a D-U-N-S number identifying PiE.
2. Create an Apple Business Manager account.
3. Create a managed Apple ID under that account.
4. Join the Apple Developer Program with the new Apple ID as a nonprofit or educational institution.
5. Apply for a nonprofit fee waiver.
6. On a Mac, create a certificate request using the Certificate Assistant and save it to the disk.
7. In the developer portal, upload the request to generate a Developer ID certificate.
8. Download the generated certificate.
9. Add the path to the certificate to electron-builder’s config.

Electron-builder should handle the rest.