Add snippet url to webhook payload

What does this MR do and why?

Add snippet url to webhook payload

All other type of note event payloads had a url in them except for snippet.

Changelog: added

Screenshots or screen recordings

How to set up and validate locally

1. Add a webhook on this link to capture events. Make sure to check Comments in the Trigger section to receive comment events.
2. Create a new snippet and comment on it.
3. Check the logs at this link. Click on Edit next to the created webhook in Step 1
4. Scroll down to see the latest webhook and click on Recent Details. You should see the added url field inside snippet

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.