Vega 5 hello world

spec.json

{
  "$schema": "https://vega.github.io/schema/vega/v5.json",
  "width": 400,
  "height": 200,
  "data": [
    {
      "name": "table",
      "values": [
        {"date": "2020-08-01", "count": 2109},
        {"date": "2020-08-02", "count": 1201},
        {"date": "2020-08-03", "count": 876},
        {"date": "2020-08-04", "count": 567},
        {"date": "2020-08-05", "count": 432},
        {"date": "2020-08-06", "count": 502},
        {"date": "2020-08-07", "count": 433},
        {"date": "2020-08-08", "count": 321},
        {"date": "2020-08-09", "count": 299},
        {"date": "2020-08-10", "count": 120}
      ]
    }
  ],
  "scales": [
    {
      "name": "xscale",
      "type": "band",
      "domain": {"data": "table", "field": "date"},
      "range": "width",
      "padding": 0.05,
      "round": true
    },
    {
      "name": "yscale",
      "domain": {"data": "table", "field": "count"},
      "nice": true,
      "range": "height"
    }
  ],
  "axes": [
    { "orient": "bottom", "scale": "xscale" },
    { "orient": "left", "scale": "yscale" }
  ],
  "marks": [
    {
      "type": "rect",
      "from": {"data":"table"},
      "encode": {
        "enter": {
          "x": {"scale": "xscale", "field": "date"},
          "width": {"scale": "xscale", "band": 1},
          "y": {"scale": "yscale", "field": "count"},
          "y2": {"scale": "yscale", "value": 0}
        },
        "update": {
          "fill": {"value": "steelblue"}
        },
        "hover": {
          "fill": {"value": "red"}
        }
      }
    }
  ]
}