* fix: do not add attributes or html elements to custom elements before they are created
Due to the way browsers treat custom elements, they are not allowed to add attributes and/or child elements upon creation. They must wait until the `connectedCallback`. That means any controller that wants to add elements should also wait until the host is connected (`hostConnected`).
* test: add generic tests for rte block elements
* chore: cleanup imports
34cad5ffef