Get rid of server-side HTML rendering

[AnttiMK]

I would like to be able to..

Have Plan serve static HTML files that wouldn't have any server-side rendering/placeholder replacement done to them. I'd also like to develop the frontend independently without having to rely on/modify the code for the backend to make changes in the frontend.

The implementation would require (at least)

• a handful of new JSON API endpoints that would serve data about different things like extensions, plugin versions etc.
• JavaScript code on the frontend that would render the JSON data into actual HTML
• code on the backend that would render all gathered data to JSON

Is your feature request related to a problem? Please describe.

The current frontend implementation relies on the backend for rendering many HTML elements, including many placeholder strings, the version check button & modal and most notably, all HTML for the plugin data extensions. The system is rather intertwined, making changing/developing the frontend rather hard due to many components relying on the backend to be displayed.

A new system that served 100% of the data via a JSON API would allow the frontend to be developed separately from the data gathering backend, making it easier to edit & render HTML on the client side. Additionally, Plan could be used as a REST API by other software, providing data to other programs/plugins if needed.