[Monorepo] Setup Jitpack

[dratwas]

Description

This is a part of migration gutenberg-mobile to gutenberg repo.

In this PR I moved jitpack.yml file to the root level.

According to documentation https://jitpack.io/docs/BUILDING/ -> Custom commands

You can create a jitpack.yml file in the root of your repository and override the build commands:

I also changed yarn to npm in the jitpack script that builds the JS bundle.

How has this been tested?

• change submodule URL in Wordpress-Android to gutenberg repo
• checkout to the latest commit on the branch from this PR
• set wp.BUILD_GUTENBERG_FROM_SOURCE = false in gradle.properites file
• The app should build without issues

Types of changes

move jitpack.yml to the root level and fix jitpack build scripts

Checklist:

• My code is tested.
• My code follows the WordPress code style.
• My code follows the accessibility standards.
• My code has proper inline documentation.
• I've included developer documentation if appropriate.
• I've updated all React Native files affected by any refactorings/renamings in this PR. .