add gitlab ci

Trying to add GitLab CI in order to release gcli binaries, but apparently the cache does not work.

.gitlab-ci.yml

+# This file is adapted from GitLab template for Rust projects
+
+# Official language image. Look for the different tagged releases at:
+# https://hub.docker.com/r/library/rust/tags/
+image: "rust:latest"
+
+# Optional: Install a C compiler, cmake and git into the container.
+# You will often need this when you (or any of your dependencies) depends on C code.
+# before_script:
+#   - apt-get update -yqq
+#   - apt-get install -yqq --no-install-recommends build-essential
+
+build:
+  stage: build
+  image: rust
+  script:
+    - cargo build --release
+  artifacts:
+    paths:
+      - target/release/gcli