v6.3.0-rc.0

Storybook 6.3 is in RC!! 🎉🎉🎉

Hundreds of improvements and fixes, including:

• Angular - Angular12, Ivy, overhauled docs support.
• Web-components - Lit2 support.
• Essentials - New measure/outline addons for CSS debugging.
• Addon API - Keyboard shortcuts for addons. Initial support in viewports, toolbars.
• Webpack 5 - Official support.
• Vite builder - Community support.
• Modern ESM - Modern package distribution.

Track the release in the Github: Storybook 6.3 Release 🛠