This PR makes a few API updates to @remote-ui/core that fix some long-standing annoyances I have had with the APIs. You can see the important part of this change in the updated packages/core/src/types.ts file, but the overall goal was to get some slightly shorter names for common API methods, and to try to align closer to modern DOM APIs:

• RemoteParent.appendChild is deprecated, with a new RemoteParent.append API recommended instead. This new API matches the DOM’s version; it allows you to pass multiple children, including strings that are converted to text nodes.
• RemoteParent.insertChildBefore is deprecated, with a new RemoteParent.insertBefore API recommended instead. This matches the DOM, including the fact that the second argument can be null (in which case, the method behaves the same as append
• RemoteParent.replaceChildren is new, and matches the DOM's API of the same name. It allows passing any number of children/ strings, and those are used to fully replace the existing children.
• RemoteText.updateText is deprecated in favor of a new RemoteText.update method, which is simply shorter.

cc/ @developit