Add a script for initializing a sealious app

Summary:
Ref T2740 - The execution of cli.js should clone and install the dependencies of the Sealious-playground on the execution folder. package.json includes a "bin" line, so when uploaded to npm will interact with the "npm init" command.

To review: cli.js installs the correct files and dependencies

Reviewers: #testers, kuba-orlik

Reviewed By: #testers, kuba-orlik

Subscribers: kuba-orlik

Maniphest Tasks: T2740

Differential Revision: https://hub.sealcode.org/D1398