Update add_to_project.yml

.github/workflows/add_to_project.yml

-name: Add all issues to F# project, assign milestone and labels
+name: Add all issues and PRs to F# project, assign milestone and labels
 
 on:
   issues:
     types:
       - opened
       - transferred
+  pull_request:
+    types:
+      - opened
 
 permissions:
   issues: write
@@ -38,6 +41,7 @@ jobs:
           github-token: ${{ secrets.REPO_PROJECT_PAT }}
   apply-label:
     runs-on: ubuntu-latest
+    if: github.event_name != 'pull_request'
     steps:
       - uses: actions/github-script@v6
         with:
@@ -50,6 +54,7 @@ jobs:
             })
   apply-milestone:
     runs-on: ubuntu-latest
+    if: github.event_name != 'pull_request'
     steps:
       - uses: actions/github-script@v6
         with: