Try add a beta workflow

This isn't very nice to be honest.

.github/workflows/beta.yaml

@@ -0,0 +1,42 @@
+# Run tests using the beta Rust compiler
+
+name: Beta Rust
+
+on:
+  workflow_call:
+    inputs:
+      tests:
+        description: "Reusable workflow of the tests to be executed using the beta compiler"
+        type: string
+        required: true
+
+env:
+  IROH_FORCE_STAGING_RELAYS: "1"
+
+jobs:
+  tests:
+    uses: "${{ inputs.tests }}"
+    with:
+      rust-version: beta
+  notify:
+    needs: tests
+    if: ${{ always() }}
+    runs-on: ubuntu-latest
+    steps:
+      - name: Extract test results
+        run: |
+          printf '${{ toJSON(needs) }}\n'
+          result=$(echo '${{ toJSON(needs) }}' | jq -r .tests.result)
+          echo TESTS_RESULT=$result
+          echo "TESTS_RESULT=$result" >>"$GITHUB_ENV"
+      - name: Notify discord on failure
+        uses: n0-computer/discord-webhook-notify@v1
+        if: ${{ env.TESTS_RESULT == 'failure' }}
+        with:
+          text: "Beta Rust in **${{ github.repository }}**:"
+          severity: error
+          details: |
+            Rustc beta tests failed
+            See https://github.com/${{ github.repository }}/actions/worklows/${{ github.workflow }}
+          webhookUrl: ${{ secrets.DISCORD_N0_GITHUB_CHANNEL_WEBHOOK_URL }}
+