Add gitlab CI

.gitlab-ci.yml

+build:
+  image: docker.io/library/rust:1-alpine
+  stage: build
+  script:
+    - cargo build --release --no-default-features
+    - mv target/release/matrix-calver matrix-calver
+  artifacts:
+    paths:
+      - matrix-calver
+    expose_as: matrix-calver