tutorial: add info about app bundle size limit

Update the tutorial on Compose Apps with an info about the limit on
size of the compose app bundle (effectively the app directory).

Signed-off-by: Mike Sul <mike.sul@foundries.io>

source/tutorials/compose-app/compose-app-docker-compose-apps.rst

@@ -12,7 +12,9 @@ This is the file structure responsible for creating the Docker Compose App:
 The combination of a top-level directory containing ``docker-compose.yml``
 will end-up in a Docker Compose App.
 
-The ``docker-compose.yml`` file specifies one or more containers to run and their configurations. 
+The ``docker-compose.yml`` file specifies one or more containers to run and their configurations.
+In addition, the Compose App directory can contain complementary files, such as configuration files, volume data, scripts, etc.
+The overall maximum allowed size of the Compose App directory is 1 GB.
 
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