Fire a rule only when a specific webform has been submitted
I got this to work but i don't know if my answer will be the best approach for what i need:

Let's say, we want the rule to be fired ONLY for the webform ID: "contact"

1) EVENT: After saving a new webform submission (rules_entity_insert:webform_submission)

2) CONDITION: Data Comparision; 

Data to compare: webform_submission.webform_id.target_id; 

Operator: ==

Value: contact

3) ACTION: Show a message on the site.

Hope it will help somebody else as well, especially that there is no documentaion yet for rules 8.

Cheers,