Support for external automation UI #852
Description
When using Playnite Web for remote control of a game library, there may to access controls that are not directly related to the game library; e.g., volume control. The needs of what these controls actually are will be different across users and even user libraries. For this reason, there cannot be a built in UI to accomodate these controls.
However, I'm thinking users can use the account settings to configure one or more external UIs. Each UI would show up in the main navigation for the specific library. In order to see these menu items, the user must be authenticated and authorized (own the library). The navigation items can be configured to either navigate to a URL or open an URL (iframed) into a modal.
This would allow users to configure external automation dashboards/UIs that could be consolidated into Playnite Web. Below is an example use case pulled from my own usage of Playnite Web. Here I have a automation UI to control the volume, either via a preset or manually, lights, and TV. This is coming from a Home Assistant dashboard.
