Fix error on Github Action "No usable version of libssl was found" with Install OpenSSL (Ubuntu only)

Author: Jose A. Fernandez

src/.github/workflows/dotnet-core.yml

@@ -26,6 +26,9 @@ jobs:
             test-framework: 'net481'
     steps:
       - uses: actions/checkout@v2
+      - name: Install OpenSSL (Ubuntu only)
+        if: runner.os == 'Linux'
+        run: sudo apt-get update && sudo apt-get install -y libssl-dev
       - name: Setup .NET
         uses: actions/setup-dotnet@v3
         with: