Update release notes for v1.19.0

Added new features and improvements for ado2gh rewire-pipeline.

Author: georgy-gorelko

releasenotes/v1.19.0.md

@@ -1 +1,3 @@
-- **ado2gh rewire-pipeline**: Migration now preserves all original trigger configurations (pullRequest, continuousIntegration, etc.) from Azure DevOps pipelines.
+- **ado2gh rewire-pipeline**: Migration now preserves all original trigger configurations (pullRequest, continuousIntegration, etc.) from Azure DevOps pipelines.
+- **ado2gh rewire-pipeline --dry-run --monitor-timeout-minutes 45**: Migration now supports a test mode to validate AzureDevOps pipeline is validated temporary rewiring to GitHub with status reported
+- **ado2gh rewire-pipeline**: New argument --ado-pipeline-idis supported for rewiring process vs pipeline name argument to ensure smoother migration where pipeline name can be ambiguous