update CI with more phases

Signed-off-by: Ava Hahn <ava@aidanis.online>

.gitlab-ci.yml

@@ -1,6 +1,20 @@
 default:
   image: rust:latest
 
+fmt:
+  stage: lint
+  script:
+    - rustfmt --check tests/*
+    - rustfmt --check src/*.rs
+    - rustfmt --check src/stl/*
+    - rustfmt --check src/bin/*
+
+lint:
+  stage: lint
+  script:
+    - cargo clippy
+  allow_failure: true
+  
 compile:
   stage: build
   script: