Give permissions to write (#687)

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# Summary

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Try to make the build preview work again
---

<!-- Add, if any, the related issue here, e.g. #6 -->

**Related issue :** #685

.github/workflows/build_pr_preview.yml

@@ -8,7 +8,8 @@ on:
     # Run when label is added or present and when pushing to the PR
     types: [labeled, opened, synchronize]
 
-permissions: read-all
+permissions:
+  contents: write
 
 jobs:
   build_preview: