Increase shared memory size for feature specs

Prior to increasing the shared memory size or `shm_size`, we received
errors trying to run feature specs due to lack of memory.

Co-authored-by: An Stewart <[email protected]>

docker-compose.yml

@@ -18,6 +18,7 @@ services:
       - postgres:/var/lib/postgresql/data:cached
 
   app:
+    shm_size: '256mb'
     build:
       context: .dockerdev
       dockerfile: Dockerfile