Update CHANGELOG

Author: mbostock

CHANGELOG.md

@@ -18,7 +18,7 @@ Plot.plot({
 })
 ```
 
-For non-gridded or sparse data, the raster and contour marks implement a variety of spatial interpolation methods to populate the raster grid. The *barycentric* interpolation method, shown below with data from the [Great Britain aeromagnetic survey](https://www.bgs.ac.uk/datasets/gb-aeromagnetic-survey/), uses barycentric coordinates from a Delaunay triangulation of the samples (small black dots).
+For non-gridded or sparse data, the raster and contour marks implement a variety of [spatial interpolation methods](./README.md#spatial-interpolation) to populate the raster grid. The *barycentric* interpolation method, shown below with data from the [Great Britain aeromagnetic survey](https://www.bgs.ac.uk/datasets/gb-aeromagnetic-survey/), uses barycentric coordinates from a Delaunay triangulation of the samples (small black dots).
 
 [<img src="./img/ca55.webp" width="650" alt="A map showing the varying intensity of the magnetic field as periodically observed from an airplane flying in an approximate grid pattern">](https://observablehq.com/@observablehq/plot-raster)
 
@@ -37,9 +37,21 @@ Plot.plot({
 })
 ```
 
-TK, alternate visualization as contours.
+The same data, as filled contours in projected coordinates:
 
-Naturally, the raster and contour mark work with Plot’s [projection system](./README.md#projection-options), allowing spatial samples to be shown in any geographic projections and in conjunction with other geographic data. The *equirectangular* projection is the natural choice for this gridded water vapor data from [NASA Earth Observations](https://neo.gsfc.nasa.gov/view.php?datasetId=MYDAL2_M_SKY_WV&date=2022-11-01).
+[<img src="./img/ca55-contours.webp" width="650" alt="A map showing the varying intensity of the magnetic field as periodically observed from an airplane flying in an approximate grid pattern">](https://observablehq.com/@observablehq/plot-raster)
+
+```js
+Plot.plot({
+  width: 640,
+  height: 484,
+  projection: {type: "reflect-y", domain: {type: "MultiPoint", coordinates: ca55.map((d) => [d.GRID_EAST, d.GRID_NORTH])}},
+  color: {type: "diverging", legend: true},
+  marks: [Plot.contour(ca55, {x: "GRID_EAST", y: "GRID_NORTH", fill: "MAG_IGRF90", stroke: "currentColor", blur: 2})]
+})
+```
+
+Naturally, the raster and contour mark support Plot’s [projection system](./README.md#projection-options), allowing spatial samples to be shown in any geographic projection and in conjunction with other geographic data. The *equirectangular* projection is the natural choice for this gridded global water vapor dataset from [NASA Earth Observations](https://neo.gsfc.nasa.gov/view.php?datasetId=MYDAL2_M_SKY_WV&date=2022-11-01).
 
 [<img src="./img/water-vapor.png" width="650" alt="A map of global atmospheric water vapor, showing a higher concentration of water vapor near the equator">](https://observablehq.com/@observablehq/plot-raster)