[Vega-Lite] 3.1 HTML setup
This example shows a minimal HTML setup for embedding a Vega-Lite visualization, loading a specification from an external JSON file. The page includes a single `<div id="vis">` container and uses the Vega, Vega-Lite, and Vega-Embed libraries from a CDN. The `vegaEmbed` function attaches the chart defined in `line.vl.json` to that container, with errors logged to the console via `catch(console.warn)`. The code relies on standard HTML and JavaScript without any framework.