Vega - how to draw x=y line?

I need to draw line x=y on the chart below. Can you help me please? It must work even if for example max(x) = 100 and max(y) = 10. We have to take the max value of x and y and draw a line from (0,0) to (max,max)

The code below takes values and sort x and y ascending and draw a chart.

Please have a look here

I know a bit of Vega Lite, however Vega is a different level ;)

{
  "$schema": "https://vega.github.io/schema/vega/v5.json",
  "background": "white",
  "padding": 5,
  "width": 200,
  "height": 200,
  "style": "cell",
  "data": [
    {
      "name": "source_0",
      "values": [
        {"x": 1, "y": 3.2},
        {"x": 2, "y": 1.9},
        {"x": 4, "y": 2.1},
        {"x": 3, "y": 4.5},
        {"x": 6, "y": 5.1},
        {"x": 5, "y": 8.5},
        {"x": 7, "y": 6},
        {"x": 8, "y": 7.9},
        {"x": 9, "y": 9.1},
        {"x": 10, "y": 11}
      ],
      "transform": [
        {
          "type": "window",
          "params": [null],
          "as": ["row"],
          "ops": ["row_number"],
          "fields": [null],
          "sort": {"field": [], "order": []}
        },
        {"type": "collect", "sort": {"field": "y"}},
        {"type": "extent", "field": "x", "signal": "extentX"},
        {"type": "extent", "field": "y", "signal": "extentY"}
      ]
    },
    {
      "name": "data_0",
      "source": "source_0",
      "transform": [
        {"type": "collect", "sort": {"field": "x"}},
        {
          "type": "formula",
          "expr": "pluck(data('source_0'),'y')[datum.row-1]",
          "as": "newY"
        }
      ]
    },
    {
      "name": "data_1",
      "source": "data_0",
      "transform": [
        {
          "type": "filter",
          "expr": "isValid(datum[\"x\"]) && isFinite(+datum[\"x\"]) && isValid(datum[\"y\"]) && isFinite(+datum[\"y\"])"
        }
      ]
    },
    {
      "name": "data_2",
      "values": [{"x": 0, "y": 0}, {"x": 1, "y": 1}],
      "transform": [
        {"type": "formula", "as": "x", "expr": "datum.x==1?max(extentX[1],extentY[1]):datum.x"},
        {"type": "formula", "as": "y", "expr": "datum.y==1?max(extentX[1],extentY[1]):datum.y"}
      ]
    }
  ],
  "marks": [
    {
      "name": "layer_0_marks",
      "type": "line",
      "style": ["line"],
      "sort": {"field": "datum[\"x\"]"},
      "from": {"data": "data_0"},
      "encode": {
        "update": {
          "stroke": {"value": "#4c78a8"},
          "x": {"scale": "x", "field": "x"},
          "y": {"scale": "y", "field": "newY"}
        }
      }
    },
    {
      "type": "line",
      "from": {"data": "data_2"},
      "encode": {
        "update": {
          "stroke": {"value": "red"},
          "x": {"scale": "x", "field": "x"},
          "y": {"scale": "y", "field": "y"}
        }
      }
    },
    {
      "name": "layer_1_marks",
      "type": "symbol",
      "style": ["point"],
      "from": {"data": "data_1"},
      "encode": {
        "update": {
          "opacity": {"value": 1},
          "fill": {"value": "#4c78a8"},
          "ariaRoleDescription": {"value": "point"},
          "description": {
            "signal": "\"x: \" + (format(datum[\"x\"], \"\")) + \"; y: \" + (format(datum[\"y\"], \"\"))"
          },
          "x": {"scale": "x", "field": "x"},
          "y": {"scale": "y", "field": "newY"}
        }
      }
    }
  ],
  "scales": [
    {
      "name": "x",
      "type": "linear",
      "domain": {
        "fields": [
          {"data": "data_0", "field": "x"},
          {"data": "data_1", "field": "x"}
        ]
      },
      "range": [0, {"signal": "width"}]
    },
    {
      "name": "y",
      "type": "linear",
      "domain": {
        "fields": [
          {"data": "data_0", "field": "y"},
          {"data": "data_1", "field": "y"}
        ]
      },
      "range": [{"signal": "height"}, 0],
      "nice": true,
      "zero": true
    }
  ],
  "axes": [
    {
      "scale": "x",
      "orient": "bottom",
      "gridScale": "y",
      "grid": true,
      "tickCount": {"signal": "ceil(width/40)"},
      "domain": false,
      "labels": false,
      "aria": false,
      "maxExtent": 0,
      "minExtent": 0,
      "ticks": false,
      "zindex": 0
    },
    {
      "scale": "y",
      "orient": "left",
      "gridScale": "x",
      "grid": true,
      "tickCount": {"signal": "ceil(height/40)"},
      "domain": false,
      "labels": false,
      "aria": false,
      "maxExtent": 0,
      "minExtent": 0,
      "ticks": false,
      "zindex": 0
    },
    {
      "scale": "x",
      "orient": "bottom",
      "grid": false,
      "title": "x",
      "labelFlush": true,
      "labelOverlap": true,
      "tickCount": {"signal": "ceil(width/40)"},
      "zindex": 0
    },
    {
      "scale": "y",
      "orient": "left",
      "grid": false,
      "title": "y",
      "labelOverlap": true,
      "tickCount": {"signal": "ceil(height/40)"},
      "zindex": 0
    }
  ]
}