Support embedding in a Shadow DOM

[kozi]

It would be very helpful if the editor supported embedding
within a Shadow DOM. This would greatly simplify the creation
of web components and make it easier to integrate
the editor into other web components.

I believe only a few adjustments would be needed:

• Styles should be injected into the Shadow DOM.
• Some event listeners should be registered within the Shadow DOM instead of on the global document.

Related issues: #30 #40

[panphora]

This is addressed in v2.0.0, just released. The web component with full Shadow DOM support is now available. Please test and open a new issue if you encounter any problems.