update CHANGELOG

Author: mbostock

CHANGELOG.md

@@ -44,7 +44,7 @@ The new [*sort* options](https://github.com/observablehq/plot/blob/main/README.m
 Plot.barY(alphabet, {x: "letter", y: "frequency", sort: {x: "y", reverse: true}})
 ```
 
-Color scales now support the *threshold* scale type, allowing you to specify a set of *n* - 1 discrete (typically numeric) thresholds to produce *n* discrete colors.
+Color scales now support the *threshold* scale type, allowing you to specify a set of *n* - 1 discrete (typically numeric) thresholds to produce *n* discrete colors. The new *quantile* color scale type will automatically compute *n* - 1 thresholds for *n* quantiles based on the data.
 
 <img width="640" alt="a histogram showing the forecast probabilities of Democratic electoral votes in the 2016 U.S. presidential election, with outcomes of 270 votes highlighted in blue" src="https://user-images.githubusercontent.com/230541/130157825-0624447b-f39d-4a2a-9363-e18129d6f20e.png">
 
@@ -58,14 +58,12 @@ Plot.plot({
     domain: [270]
   },
   marks: [
-    Plot.ruleX(data, {x: "dem_electoral_votes", y: "probability",stroke: "dem_electoral_votes",strokeWidth: 1.5}),
+    Plot.ruleX(data, {x: "dem_electoral_votes", y: "probability", stroke: "dem_electoral_votes", strokeWidth: 1.5}),
     Plot.ruleX([270])
   ]
 })
 ```
 
-The new *quantile* color scale type will automatically compute *n* - 1 thresholds for *n* quantiles based on the data.
-
 Diverging color scales now support transformations via four new scale types: *diverging-sqrt*, *diverging-pow*, *diverging-log*, and *diverging-symlog*, corresponding to the *sqrt*, *pow*, *log*, and *symlog* quantitative scale types respectively.
 
 Diverging scales now support a *symmetric* option, which defaults to true, to ensure that differences above and below the pivot are equally apparent. (This assumes that the diverging scale’s interpolator is similarly symmetric; this is true of all the built-in diverging color schemes from ColorBrewer.) For example, the choropleth below exaggerates West Virginia’s population decline of −3% relative to Alaska’s gain of +3%. This exaggeration is caused by the domain of [−3%, +17%]: −3% is mapped to the darkest purple while +17% is mapped to the darkest green. (The pivot of 0 is mapped to the midpoint of the scheme, which is light gray here.)