ci: fix wrong path filter

Author: ElstaraNova

.github/workflows/deploy-doc.yaml

@@ -3,11 +3,23 @@ on:
   push:
     branches:
       - master
-    path:
-      - "doc/**"
 
 jobs:
+  changes:
+    runs-on: ubuntu-latest
+    outputs:
+      doc: ${{ steps.filter.outputs.doc }}
+    steps:
+    - uses: actions/checkout@v2
+    - uses: dorny/paths-filter@v2
+      id: filter
+      with:
+        filters: |
+          doc:
+            - 'doc/**'
   deploy:
+    needs: changes
+    if: ${{ needs.changes.outputs.doc == 'true' }}
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v2