How to get metadata like tags, skill in ticket for a Voice call using digital line

I recently integrated calling feature on my website following this article
https://developer.zendesk.com/documentation/zendesk-web-widget-sdks/sdks/web/voice-messaging-qs/

Where an agent can click a button and initiate a call to some agent. Now the call when picked up creates a ticket in zendesk I want to know how to pass some metadata in javascript so when the ticket is created those things can be seen by agent to help customer more effectively 

I am using this js web widget library  
<script src="https://static.zdassets.com/ekr/snippet.js?key=${zendeskKey}"/>

And I invoke the voice call using 

zE('messenger:open', 'voice', '1010101010')

where the sample value 101010101 is my ZENDESK LINE ID


I need the metadata like tags and skill from the frontend because I want to use the skill based routing in omni-channel so when user chooses his native language as French the call will be routed to an agent who has "French" as his skill in skill management