workflows: add DCO verification

See openslide/openslide#355.

Author: bgilbert

.github/workflows/dco-check.yml

@@ -0,0 +1,13 @@
+name: DCO
+
+on:
+  pull_request:
+    branches: [main]
+
+permissions:
+  contents: read
+
+jobs:
+  check:
+    name: Organization
+    uses: openslide/.github/.github/workflows/dco-check.yml@main

.github/workflows/dco-report.yml

@@ -0,0 +1,15 @@
+name: DCO report
+
+on:
+  workflow_run:
+    workflows: ["DCO"]
+    types:
+      - completed
+
+permissions:
+  pull-requests: write
+
+jobs:
+  comment:
+    name: Organization
+    uses: openslide/.github/.github/workflows/dco-report.yml@main