add OSSF scorecard action (#599)

Signed-off-by: Bob Callaway <bob.callaway@gmail.com>

.github/workflows/scorecard_action.yml

+name: Scorecards supply-chain security
+on:
+  # Only the default branch is supported.
+  branch_protection_rule:
+  schedule:
+    # Weekly on Saturdays.
+    - cron: '30 1 * * 6'
+  push:
+    branches: [ main ]
+
+# Declare default permissions as read only.
+permissions: read-all
+
+jobs:
+  analysis:
+    name: Scorecards analysis
+    runs-on: ubuntu-latest
+    permissions:
+      # Needed to upload the results to code-scanning dashboard.
+      security-events: write
+      actions: read
+      contents: read
+
+    steps:
+      - name: "Checkout code"
+        uses: actions/checkout@ec3a7ce113134d7a93b817d10a8272cb61118579 # v2.4.0
+        with:
+          persist-credentials: false
+
+      - name: "Run analysis"
+        uses: ossf/scorecard-action@0fe1afdc40f536c78e3dc69147b91b3ecec2cc8a
+        with:
+          results_file: results.sarif
+          results_format: sarif
+          # Read-only PAT token. To create it,
+          # follow the steps in https://github.com/ossf/scorecard-action#pat-token-creation.
+          repo_token: ${{ secrets.SCORECARD_TOKEN }}
+          # Publish the results for public repositories to enable scorecard badges. For more details, see
+          # https://github.com/ossf/scorecard-action#publishing-results.
+          # For private repositories, `publish_results` will automatically be set to `false`, regardless
+          # of the value entered here.
+          publish_results: true
+
+      # Upload the results as artifacts (optional). Commenting out will disable uploads of run results in SARIF
+      # format to the repository Actions tab.
+      - name: "Upload artifact"
+        uses: actions/upload-artifact@82c141cc518b40d92cc801eee768e7aafc9c2fa2 # v2.3.1
+        with:
+          name: SARIF file
+          path: results.sarif
+          retention-days: 5
+
+      # Upload the results to GitHub's code scanning dashboard.
+      - name: "Upload to code-scanning"
+        uses: github/codeql-action/upload-sarif@5f532563584d71fdef14ee64d17bafb34f751ce5 # v1.0.26
+        with:
+          sarif_file: results.sarif