update CHANGELOG

Author: mbostock

CHANGELOG.md

@@ -71,7 +71,7 @@ Plot.plot({
 })
 ```
 
-Diverging scales now support a *symmetric* option, which defaults to true, to ensure that differences above and below the pivot are equally apparent. For example, the choropleth below gives equal visual weight to West Virginia’s population decline of −3% and Alaska’s gain of +3%. If *symmetric* is false, as before, then -3% is mapped to the darkest purple. (Diverging scales should always use balanced interpolators where the negative and positive extremes have equal weight; this is true of Plot’s built-in diverging color schemes from ColorBrewer.)
+Diverging scales now support a *symmetric* option, which defaults to true, to ensure that differences above and below the pivot are equally apparent. For example, the choropleth below gives equal visual weight to West Virginia’s population decline of −3% and Alaska’s gain of +3%. If *symmetric* is false, as before, then −3% is mapped to the darkest purple. (Diverging scales should always use balanced interpolators where the negative and positive extremes have equal weight; this is true of Plot’s built-in diverging color schemes from ColorBrewer.)
 
 <img width="641" alt="a choropleth with symmetric diverging scale, showing the change in population of the fifty U.S. states between 2010 and 2019; the change in negative values is commensurate with the change in positive values" src="https://user-images.githubusercontent.com/230541/129834634-2617a895-5040-4135-b015-0aa4b812c262.png">
 
@@ -97,7 +97,7 @@ Plot.plot({
 
 ### Facets
 
-The mark *facet* option can be used to control whether or not a mark is faceted. The supported values are *auto*, *include*, and *exclude*. True is an alias for *include* and null (and false) disables faceting. The default is *auto*, which facets a mark if and only if its data is strictly equal to the facet data. The *include* facet mode allows a mark with different data to be faceted; however, it requires that the mark’s data be parallel with the facet data (*i.e.*, have the same length and order). The *exclude* facet mode shows all data that are not present in the current facet; this can provide shared context across facets without overdrawing.
+The mark *facet* option can be used to control whether or not a mark is faceted. The supported values are *auto*, *include*, *exclude*, and null. True is an alias for *include* and false is an alias for null. The default is *auto*, which facets a mark if and only if its data is strictly equal to the facet data. The *include* facet mode allows a mark with different data to be faceted; however, it requires that the mark’s data be parallel with the facet data (*i.e.*, have the same length and order). The *exclude* facet mode shows all data that are not present in the current facet; this can provide shared context across facets without overdrawing. The null mode disables faceting, replicating the mark across all facets.
 
 <img width="640" alt="a faceted scatterplot showing the correlation between culmen depth and length across sex and species; each facet shows the current sex and species with black dots and all other penguins as pale gray dots" src="https://user-images.githubusercontent.com/7001/130275538-ec33aaa4-73e2-4fb3-862a-8fdd47a788d6.png">