A simple line chart shows the change in a quantitative "rate" over temporal "steps" using a single line mark. It loads its data from a remote GitHub gist URL, and the chart is defined as a Vega-Lite specification in `line.vl.json`. The visualization is rendered by the Vega-Lite and Vega libraries, embedded into the page via `vegaEmbed`. The chart is configured with a fixed width of 360 pixels, encoding the steps field on the x-axis and the rate field on the y-axis.