Allow gh-ph to run on PRs from forks

[1] https://docs.github.com/en/actions/using-workflows/events-that-trigger-workflows#pull_request_target

Author: Frederick888

.github/workflows/gh-ph.yml

@@ -1,7 +1,11 @@
 name: Pull request history
 
 on:
-  pull_request:
+  pull_request_target:
+
+permissions:
+  contents: read
+  pull-requests: write
 
 jobs:
   gh-ph: