chore(ci): rework docker hub description workflow

- Run only on base repository
- Rename job from `dockerHubDescription` to `docker-hub-description`
- Limit permissions of job to read only
- Remove unneeded names for steps

.github/workflows/dockerhub-description.yml

@@ -1,18 +1,22 @@
 name: Docker Hub description
 on:
   push:
-    branches: [master]
+    branches:
+      - master
     paths:
       - README.md
       - .github/workflows/dockerhub-description.yml
 jobs:
-  dockerHubDescription:
+  docker-hub-description:
+    if: github.repository == 'qdm12/gluetun'
     runs-on: ubuntu-latest
+    permissions:
+      actions: read
+      contents: read
     steps:
-      - name: Checkout
-        uses: actions/checkout@v3
-      - name: Docker Hub Description
-        uses: peter-evans/dockerhub-description@v3
+      - uses: actions/checkout@v3
+
+      - uses: peter-evans/dockerhub-description@v3
         with:
           username: qmcgaw
           password: ${{ secrets.DOCKERHUB_PASSWORD }}