Add basic gitlab yaml for releasing extension

.gitlab-ci.yml

+stages:
+  - release
+
+Upload release to TER:
+  stage: release
+  image: composer:1
+  only:
+    - tags
+  before_script:
+    - apk add libxml2-dev php-soap
+    - docker-php-ext-install soap
+    - composer global require namelesscoder/typo3-repository-client
+  script:
+    - >
+      if [ -n "$CI_COMMIT_TAG" ] && [ -n "$T3O_USERNAME" ] && [ -n "$T3O_PASSWORD" ]; then
+        echo -e "Preparing upload of release ${CI_COMMIT_TAG} to TER\n"
+        # Cleanup before we upload
+        git reset --hard HEAD && git clean -fx
+        # Upload
+        TAG_MESSAGE=`git tag -n10 -l $CI_COMMIT_TAG | sed 's/^[0-9.]*[ ]*//g'`
+        echo "Uploading release ${CI_COMMIT_TAG} to TER"
+        .Build/bin/upload . "$T3O_USERNAME" "$T3O_PASSWORD" "$TAG_MESSAGE"
+      fi;