ci: Update auto-label workflow to use pull_request_target (#323)

Author: BigLep

.github/workflows/auto-label.yml

@@ -3,7 +3,9 @@ name: Auto-label issues and PRs
 on:
   issues:
     types: [opened]
-  pull_request:
+  # We do pull_request_target instead of pull_request to support PR's from forks.  
+  # This is safe here because we're not checking out or executing any code from the fork; we're just adding labels.
+  pull_request_target:
     types: [opened]
 
 jobs:
@@ -30,4 +32,4 @@ jobs:
               owner: context.repo.owner,
               repo: context.repo.repo,
               labels: ['team/fs-wg', 'team/filecoin-pin']
-            })
+            })