Migrate from Custom UI to Lovelace UI

[renemarc]

As a developer, I want to migrate to Lovelace UI so that I can keep up with modern times.

Acceptance criteria

1. It's done when Most Custom UI elements have found a Lovelace UI equivalent.
2. It's done when Lovelace UI is a first-class citizen in in this configuration.

Additional details

• https://demo.home-assistant.io/#/lovelace/0
• https://community.home-assistant.io/t/my-lovelace-plugins/70726