Sign windows executable

[willwade]

We want to sign our Windows builds so that when a user opens up EyeCommander on Windows it says that the publisher is 'Ace Centre' rather than 'Unknown'

This process should be automated so the builds are automatically signed before they are published.

Notes:

• Existing Github action step that outputs our cert to a .pfx file
• Electron forge docs on how to sign a windows build