Add faceting section to gallery for pie charts section (#322)

Added section on faceting pie charts with example code.

Author: EvaMaeRey

doc/gallery/examples/pie-chart.qmd

@@ -98,3 +98,18 @@ VISUALISE island AS fill FROM ggsql:penguins
   PROJECT TO polar SETTING start => -90, end => 90
   SCALE angle SETTING expand => 0
 ```
+
+
+### Faceting pie charts
+
+When faceting, you will typically want to pies to be whole, which requires the `SETTING free => 'angle'` specification.
+
+```{ggsql}
+VISUALISE island AS fill FROM ggsql:penguins
+  DRAW bar
+  PROJECT TO polar 
+  FACET species SETTING free => 'angle'
+```
+
+
+