Try to cache between lint/test and build stages

.gitlab-ci.yml

@@ -2,6 +2,17 @@
 # https://hub.docker.com/r/library/node/tags/
 image: node:15.0.1
 
+cache:
+  key:
+    files:
+      - package.json
+      - yarn.lock
+  untracked: true
+  paths:
+    - lib/ember-cli-kss/node_modules/
+    - lib/ember-cli-sassdoc/node_modules/
+    - node_modules/
+
 stages:
   - test
   - build