Add permissions to `post_summaries.yaml` (#149)

* Add  workflow_call:

* add permissions
diff --git a/.github/workflows/post_summaries.yaml b/.github/workflows/post_summaries.yaml
index 1f6f56d..e86914f 100644
--- a/.github/workflows/post_summaries.yaml
+++ b/.github/workflows/post_summaries.yaml
@@ -3,6 +3,7 @@
 on:
   # Trigger this workflow after the Health workflow completes. This workflow will have permissions to
   # do things like create comments on the PR, even if the original workflow couldn't.
+  workflow_call:
   workflow_run:
     workflows: [Health]
     types:
@@ -10,6 +11,8 @@
 
 jobs:
   upload:
+    permissions:
+      pull-requests: write
     runs-on: ubuntu-latest
     if: >
       github.event.workflow_run.event == 'pull_request' &&