Document to what level we require JavaScript for UI
Questions like:
- to what extent the UI should be usable with w3m, and to what extent there may be parts that require modern browners with modern JavaScript
- whether we have interface whose JS-less fallback is debusine-client
- what parts should be HTML first, with JS as progressive enhancement, and if there are parts that can be JS-only to allow a broader range of UI components for complex UI tasks