gitlab-ci: update submodules before build

Gitlab CI will cache build directory per branch and per build step. Also it doesn't try to update submodules.
We have to do this manually because otherwise we end up with old version of submodule in cached directory.

.gitlab-ci.yml

@@ -3,6 +3,9 @@ stages:
   - test
   - deploy
 
+before_script:
+  - git submodule update --init --recursive
+
 build_template_app:
   stage: build
   image: espressif/esp32-ci-env