chore: add dependency-diff workflow (#166)

This comes in useful for diffing duplicate dependencies, provenance,
etc.

Author: 43081j

.github/workflows/dependency-diff.yml

@@ -0,0 +1,18 @@
+name: Dependency Diff
+
+on:
+  pull_request:
+
+jobs:
+  diff_dependencies:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      pull-requests: write
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+        with:
+          fetch-depth: 0
+      - name: Create Diff
+        uses: e18e/action-dependency-diff@d995338f3b229fe7b2cd82048df5da930f70c7c3 # v1.4.4