Notarize MacOS releases

[skeet70]

The tool builds fine on MacOS, so installations using homebrew or otherwise building from source will work fine. Someone downloading pre-built binaries off Github Releases though won't be able to run the tool unless they bypass security rules.

We can sign and notarize our pre-built x86_64 and arm64 binaries to make them securely runnable on MacOS.

[BobWall23]

Need to see if we have the keys from the old ironssh brew publishing.

Notarization requires shipping the signed binary to Apple for approval. :sadpanda: