Explicitly state write permissions on publish job (#192)

[](https://datadoghq.atlassian.net/browse/VULN-8095)

.github/workflows/docker.yml

@@ -7,6 +7,8 @@ on:
 jobs:
   build-and-publish:
     runs-on: ubuntu-latest
+    permissions:
+      packages: write
     if: github.ref == 'refs/heads/master' || startsWith(github.ref, 'refs/tags/')
     steps:
     - uses: actions/checkout@v2