Add CI check for SUNS poster

.github/workflows/check_suns.yml

@@ -0,0 +1,31 @@
+name: QA
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+    branches:
+      - master
+  merge_group:
+    branches:
+      - master
+
+jobs:
+  check_file_dir:
+    if: ${{ !contains(github.event.head_commit.message, '[ci skip]') }}
+    name: "Check (poster/solgov/suns)"
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout Project
+        uses: actions/checkout@v4
+
+      - name: Check /obj/structure/sign/poster/solgov/suns
+        run: |
+          output=$(fgrep -i -r "/obj/structure/sign/poster/solgov/suns" .)
+          if [ -n "$output" ]; then
+              echo "Error: Found occurrences of '/obj/structure/sign/poster/solgov/suns'"
+              echo "Replace with one of:"
+              echo "    /obj/structure/sign/poster/contraband/free_tonto"
+              echo "    /obj/structure/sign/poster/contraband/roseusfilm1"
+              exit 1
+          fi