Build support for arm64

[hendricksond]

• Update electron-builder to fix build errors when building on M1 macs
• Add --x64 and --arm64 flags to builds for all platforms (including release)

These changes will generate x64 and arm64 builds for all platforms. I considered adding different build commands for targeting specific architectures per platform, but that's a bit cumbersome. Builds are done in parallel, so it's probably fine to always build for both architectures.

Fixes #96

Caveat: I ran yarn upgrade when updating electron-builder to fix an M1 build bug. I don't think this screwed anything up, but I'm not really sure how to tell. I'm not the most familiar with yarn.

My dev machine is an M1 mac, so I haven't tested the build changes from an x64 platform. But seeing how arm64 can build x64 just fine, I assume the reverse is also true.

[FormallyKnownAs]

For release 1.31, I don't know if I did something wrong but I still see it running as x64 instead of running as arm64 (kind = "Apple"). Is there a problem with the build?