[Content]: Improve docs on untrack

[atilafassina]

📚 Subject area/topic

Solid core
untrack

📋 Description of content that is out-of-date or incorrect

This page has only the type and a one-liner about what the method does.
Let's add an example use-case and a more thorough explanation.

[brenelz]

The link in the ticket didn't work for me. Should be the following:
https://docs.solidjs.com/reference/reactive-utilities/untrack

I don't feel I know enough about untrack to write about it. @devagrawal09 might be a good candidate

[atilafassina]

The link in the ticket didn't work for me. Should be the following: https://docs.solidjs.com/reference/reactive-utilities/untrack

I don't feel I know enough about untrack to write about it. @devagrawal09 might be a good candidate

thanks! It was late and forgot to add the docs. subdomain on the link 🤦