fix(build): don't run bundlesize action on PRs from forks (#11887)

.github/workflows/pr-bundlesize-compare.yml

@@ -6,6 +6,7 @@ on:
 jobs:
   # Build current and upload stats.json
   build-head:
+    if: github.event.pull_request.head.repo.full_name == github.repository
     name: "Build head"
     permissions:
       contents: read
@@ -46,6 +47,7 @@ jobs:
 
   # Build base for comparison and upload stats.json
   build-base:
+    if: github.event.pull_request.head.repo.full_name == github.repository
     name: "Build base"
     permissions:
       contents: read
@@ -86,6 +88,7 @@ jobs:
 
   # run the action against the stats.json files
   compare:
+    if: github.event.pull_request.head.repo.full_name == github.repository
     name: "Compare base & head bundle sizes"
     runs-on: ubuntu-latest
     needs: [build-base, build-head]