[gnome-bootstrap-theme] ci: install npm packages

[Guillaume Bernard <gbernard src gnome org>]

commit 103607ebfa179556c5cf93cfcefc92d32bb7f236
Author: Guillaume Bernard <associations guillaume-bernard fr>
Date:   Mon Sep 26 13:16:59 2022 +0200

    ci: install npm packages

 .gitlab-ci.yml | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index fe3e03c..7e9f34f 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -5,7 +5,8 @@ build_theme:
   stage: build
   image: alpine:latest
   script:
-    - apk add --no-cache uglify-js sassc
+    - apk add --no-cache uglify-js sassc npm
+    - npm install
     - ./build_deneb_theme.sh
   artifacts:
     name: deneb-$CI_COMMIT_BRANCH-$CI_COMMIT_REF_NAME