Add a component to directly embed html

[wwwillchen]

There's two parts:

• Embedding sanitized HTML (strips out JS)
• Embedding unsanitized HTML (includes JS) in a sandbox (iframe)

The complexity with unsanitized HTML is that Trusted Types blocks it, which means we need to either use Angular's Trusted Type policy or introduce our own Trusted Type policy. The issue is how this will work downstream (we may need to use the downstream Trusted Type policy).