add license_finder for license checks

.github/workflows/licensing.yaml

@@ -0,0 +1,21 @@
+name: Verify dependency licenses
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+    types:
+      - opened
+      - reopened
+      - synchronize
+
+jobs:
+  licensing:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+        with:
+          fetch-depth: 0
+      - run: sudo gem install license_finder
+      - run: license_finder

doc/dependency_decisions.yml

@@ -0,0 +1,31 @@
+---
+- - :permit
+  - bsd-2-clause
+  - :who:
+    :why:
+    :versions: []
+    :when: "2022-01-28 22:57:44.699976000 Z"
+- - :permit
+  - bsd-3-clause
+  - :who:
+    :why:
+    :versions: []
+    :when: "2022-01-28 22:57:47.442554000 Z"
+- - :permit
+  - apache-2.0
+  - :who:
+    :why:
+    :versions: []
+    :when: "2022-01-28 22:58:10.290944000 Z"
+- - :permit
+  - MIT
+  - :who:
+    :why:
+    :versions: []
+    :when: "2022-01-28 23:02:00.154973000 Z"
+- - :permit
+  - ISC
+  - :who:
+    :why:
+    :versions: []
+    :when: "2022-01-28 23:02:02.680050000 Z"