added Install Mono on Ubuntu step

Author: v-rachitsh

.azdo/pipelines/stages/release.yml

@@ -9,6 +9,12 @@ parameters:
   - name: RepositoryName
     default: microsoft/azure-health-data-services-toolkit
 
+steps:
+- script: |
+    sudo apt update
+    sudo apt install -y mono-complete
+  displayName: 'Install Mono on Ubuntu'
+
 stages:
   - stage: ${{ format('Signing_{0}', parameters.PackageArtifactName) }}
     displayName: 'Sign Code & Packages'