TST: Add stages to CI

.gitlab-ci.yml

@@ -23,6 +23,7 @@ stages:
 
 # Only check style for Julia 1.6 since support for 1.0 may be dropped anyway
 code-style:
+  stage: code-style
   image: julia:1.6
   tags: [ docker ]
   script:
@@ -45,6 +46,7 @@ code-style:
 # Name a test and select an appropriate image.
 # images comes from Docker hub
 test:1.0:
+  stage: test
   image: julia:1.0
   # Use `docker` runners
   tags: [ docker ]
@@ -68,6 +70,7 @@ test:1.0:
       println("(", cl/tl*100, "%) covered")'
 
 test:1.6:
+  stage: test
   image: julia:1.6
   # Use `docker` runners
   tags: [ docker ]