vl

[mbostock]

Adds the vega-lite-api to recommended libraries as vl. The equivalent JavaScript is:

import * as vega from "npm:vega";
import * as vegaLite from "npm:vega-lite";
import * as vegaLiteApi from "npm:vega-lite-api";

const vl = vegaLiteApi.register(vega, vegaLite);

[mbostock]

This ends up loading two versions of vega 😞 because [email protected] loads [email protected], whereas loading the latest version gives [email protected]. I can’t tell why that is, though… it seems to be that jsDelivr is stale in resolving the version of the vega peer dependency from vega-lite. Anyway, I think this PR is correct.

[Fil]

Nice! and, to consume a JSON spec, we can do this:

```js
function vlFromSpec(spec) {
  const div = document.createElement("div");
  const view = div.value = new vl.vega.View(vl.vega.parse(vl.vegalite.compile(spec).spec));
  return view.initialize(div).runAsync().then(() => div);
}
```

```js
display(vlFromSpec({ … spec …})
```

[Fil]

I wonder if we should expose an additional method to render from a JSON spec like I did above; but maybe there is already something in this vl object that does it and that I'm not seeing.

[mbostock]

I guess we should add vega-tooltip as a dependency… 🤔