NOTE: This PR isn't targeting master; it's targeting update-to-core-js-3

@existentialism If you want to help you can push here, just leave a comment. We'll merge this PR to the main PR (#7646) when we are done.

• ./available-plugins.js
• ./filter-items.js
• ./index.js
• ./get-option-specific-excludes.js
• ./debug.js
• ./types.js
• ./utils.js
• ./options.js
• ./targets-parser.js
• ./normalize-options.js
• ./module-transformations.js

Maybe not needed:

• ./polyfills/regenerator/entry-plugin.js
• ./polyfills/regenerator/usage-plugin.js
• ./polyfills/corejs2/entry-plugin.js
• ./polyfills/corejs2/get-platform-specific-default.js
• ./polyfills/corejs2/built-in-definitions.js
• ./polyfills/corejs2/usage-plugin.js
• ./polyfills/corejs3/entry-plugin.js
• ./polyfills/corejs3/shipped-proposals.js
• ./polyfills/corejs3/built-in-definitions.js
• ./polyfills/corejs3/usage-plugin.js