Add Benjie and Default Value Coercion RFC to Dec 2020 WG (graphql#551)

Author: benjie

agendas/2020-12-03.md

@@ -28,6 +28,7 @@ agenda, edit this file.*
 | Name                     | Organization / Project   | Location
 | ------------------------ | ------------------------ | ------------------------
 | Lee Byron                | GraphQL Foundation       | San Francisco, CA, US
+| Benjie Gillam ✏️          | Graphile                 | Southampton, UK
 | *ADD YOUR NAME ABOVE TO ATTEND*
 
 
@@ -58,4 +59,5 @@ Example agenda item:
 1. Review agenda (2m, Lee)
 1. Review previous meeting's action items (5m, Lee)
    - [All action items](https://github.com/graphql/graphql-wg/issues?q=is%3Aissue+label%3A%22Action+item+%3Aclapper%3A%22)
+1. [RFC: Default value coercion](https://github.com/graphql/graphql-spec/pull/793) (20m, Benjie)
 1. *ADD YOUR AGENDA ABOVE*