Adding latest TWiG

[doc only]

docs/appendix/twig.md

@@ -22,3 +22,4 @@ They could be release notes, documentation, hopes, dreams, or whatever: so long
 * 2020-03-09: [Metric lifetimes](https://blog.mozilla.org/data/2020/03/09/this-week-in-glean-metric-lifetimes/)
 * 2020-03-13: [Adding support for GLAM on Glean](https://blog.mozilla.org/data/2020/03/13/this-week-in-glean-adding-support-for-glam-on-glean/)
 * 2020-03-25: [Comparing Apples to Oranges](https://blog.mozilla.org/data/2020/03/25/this-week-in-glean-comparing-apples-to-oranges/)
+* 2020-04-15 [How Much Does That Data Cost](https://chuttenblog.wordpress.com/2020/04/15/this-week-in-glean-how-much-does-that-data-cost/)