chore: add workflow to comment on fork pull requests

.github/workflows/fork-pr-comment.yml

@@ -0,0 +1,38 @@
+name: Comment on fork pull requests
+
+on:
+  pull_request_target:
+    types: [opened]
+
+jobs:
+  comment:
+    name: Post fork PR comment
+    runs-on: ubuntu-latest
+    permissions:
+      pull-requests: write
+    if: github.event.pull_request.head.repo.full_name != github.repository
+    steps:
+      - name: Post comment
+        uses: actions/github-script@v7
+        with:
+          script: |
+            await github.rest.issues.createComment({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              issue_number: context.issue.number,
+              body: [
+                'Thank you for your pull request! :tada:',
+                '',
+                'We noticed that this PR was submitted from a fork. For the best experience with our CI system, we recommend contributing from a branch directly inside the **eic/EICrecon** repository.',
+                '',
+                'To do so, please consider:',
+                '1. Becoming a member of the [**eic** organization](https://github.com/eic)',
+                '2. Joining the **ePIC Devs** team within the organization',
+                '',
+                'Visit [github.com/eic](https://github.com/eic) for more information and instructions on how to join.',
+                '',
+                'Once you are a member, you will be able to push branches directly to this repository and open pull requests without needing a fork.',
+                '',
+                'Since this pull request won't be able to be assessed and merged, you are welcome to close it when you have opened a new pull request from a branch in the repository.',
+              ].join('\n')
+            });