`spectacle-cli`: Initial migration to spectacle monorepo

## What?

We'd like to move [`spectacle-cli`](https://github.com/FormidableLabs/spectacle-cli) into the spectacle monorepo. [See here](https://github.com/FormidableLabs/spectacle/wiki/Spectacle-Roadmap#spectacle-cli).

This will be a multi-step process. The goal of this ticket is to initialize a package in the spectacle monorepo for `spectacle-cli` and migrate the existing `spectacle-cli` into the monorepo.