Add .gitlab-ci.yml

.gitlab-ci.yml

+before_script:
+    - platformio init
+    - platformio update
+    - platformio upgrade
+    
+after_script:
+    - git clean -fxd
+    - git checkout .
+
+espbuildfirmware:
+  stage: build
+  script:
+    - platformio run
+ 
+archivefirmware:
+  stage: deploy
+  artifacts:
+    paths:
+      - .pioenvs/nodemcuv2/firmware.elf
+    expire_in: 1 week
+  dependencies:
+    - espbuildfirmware
+    
+# NOT YET!!!   
+#test1:
+#  stage: test
+#  script: 
+#    - echo "Do a test here"
+#    - echo "For example run a test suite"
+#   
+#test2:
+#  stage: test
+#  script: 
+#    - echo "Do another parallel test here"
+#    - echo "For example run a lint test"