feat(docs): Run Preview deployment automatically when docs changed

.gitlab-ci.yml

@@ -68,7 +68,6 @@ review_front:
 review_docs:
   interruptible: true
   stage: deploy
-  when: manual
   allow_failure: true
   image: python:3.10
   variables:
@@ -99,6 +98,12 @@ review_docs:
   environment:
     name: review/docs/$CI_COMMIT_REF_NAME
     url: http://$CI_PROJECT_NAMESPACE.pages.funkwhale.audio/-/$CI_PROJECT_NAME/-/jobs/$CI_JOB_ID/artifacts/docs-review/index.html
+  rules:
+    - if: $CI_PIPELINE_SOURCE == "merge_request_event"
+      changes:
+        - docs/**/*
+    - if: $CI_PIPELINE_SOURCE != "merge_request_event" && $CI_COMMIT_REF_NAME != $CI_DEFAULT_BRANCH
+      when: manual
 
 changelog_snippet:
   interruptible: true