add .gitlab-ci.yml

.gitlab-ci.yml

+image: platformio/platformio:latest
+
+stages:
+  - build
+
+build-client-central-mast:
+  stage: build
+  script:
+    - cd client/client_central_mast && platformio run
+
+build-client-mock:
+    stage: build
+    script:
+        - cd client/client_mock && platformio run
+
+build-client-satellite:
+    stage: build
+    script:
+        - cd client/client_satellite && platformio run
+
+build-client-esp-cam:
+    stage: build
+    script:
+        - cd client/ESPcam && platformio run
+
+build-host-central-mast:
+    stage: build
+    script:
+        - cd host/host_central_mast && platformio run
\ No newline at end of file