Include dates with no values in charts

[carlineng]

From @bporterfield:

I'm having trouble with charting and sparse data - I want to show a chart of usage across days, but using the bar chart tosses out the days that don't have data.

Here is the bar, which gives me accurate representation of the sparse usage except it skips days where there is no data, so glancing at it without paying very close attention to the X axis gives you the wrong impression

and i’m savvy enough to know how to fill the empty dates in sql with zeros but would be rad if there was easy malloy or malloy charting way to do that