This Google Cloud Function takes Salesforce Outbound Messages and forwards them to a (given) Hangouts Chat webhook with formatting applied.
gcloud functions deploy salesforceOutboundMessagesToHangoutsChat --trigger-http --allow-unauthenticated --runtime nodejs10 --region asia-northeast1
TIP: Use the following for your avatar URL: https://c1.sfdcstatic.com/content/dam/web/en_us/www/images/nav/salesforce-cloud-logo-sm.png
URLEncode your webhook URL and append it to your Cloud Function as value for the url
querystring parameter:
https://my-great-cloud-function.com/salesforceOutboundMessagesToHangoutsChat?url=<urlencoded-string-here>
Don't forget to activate the new workflow rule!