Add a snap package

[evandandrea]

Materialette looks great, so I thought I'd create a snap package in the hope that it could be added to the Snap Store. If you're willing to publish it, you would just need to create an account and register the materialette name. The file created by build:snap can then be uploaded with snapcraft push --release stable *.snap. You can get that snapcraft command with brew install snapcraft on Mac or snap install snapcraft on Linux, then snapcraft login.

Cheers!