.gitlab-ci.yml: Gitlab may display the HTML rcoverage report

Depending on the activation of Gitlab Pages (and on my
own understanding of this feature…)

.gitlab-ci.yml

@@ -83,6 +83,9 @@ algo_coverage:
   stage: coverage
   coverage: /^\s*lines\.*:\s+([0-9.]+\%)/
   script: make -C algo lcov_reports
+  artifacts:
+    paths:
+      - algo/reports/
   only:
     - /^feature-.*a.*\/.*$/