init and fetch sdk submodule before container build in GH codespaces (#4449)

Author: wvandeun

.devcontainer/onCreateCommand.sh

@@ -6,4 +6,6 @@ poetry config virtualenvs.create true
 poetry config virtualenvs.in-project true
 poetry install --no-interaction --no-ansi
 
+git submodule update --init
+
 invoke demo.build

.devcontainer/postCreateCommand.sh

@@ -1,4 +1,5 @@
 #!/bin/bash
 
 git pull
+git submodule update
 invoke demo.start --wait