Added CODEOWNERS and license-header workflow (#2)

Author: sei-aschlackman

.github/CODEOWNERS

@@ -0,0 +1 @@
+*       @cmu-sei/crucible-code-owners

.github/workflows/license-header.yml

@@ -0,0 +1,18 @@
+name: License Header Check
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+    branches:
+      - main
+
+jobs:
+  header-check:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check Headers
+        uses: cmu-sei/Crucible-Github-Actions/actions/header@header-v1.0
+        with:
+          github_token: ${{ secrets.GITHUB_TOKEN }}