Adding check for release notes being populated.

release-branch-pipeline.yml

@@ -10,6 +10,17 @@ variables:
   VERSION:
 
 steps:
+  # Checks if the release notes file is populated. Exits if it is not.
+  - bash: |
+      if [ -s RELEASE_NOTES.md ]
+      then
+            echo "RELEASE_NOTES.md has data, proceeding to next step."
+      else
+            echo "Your RELEASE_NOTES.md file is empty. Please provide release notes before creating a release."
+            exit 1
+      fi
+      displayName: 'RELEASE_NOTES.md check'
+
   # This task pulls the <version> value from the org.hl7.fhir.r5 project pom.xml file. All modules are released as 
   # the same version, at the same time, as defined in the root level pom.xml.
   - task: PowerShell@2