A little extra detail: for us to accept it as a contribution into the core component it would need to be optional, and disabled-by-default (so we don’t change the behaviour for any existing users).
In terms of implementation, topic lists already have a ‘liked’ boolean, so you could use that to decide whether the 
is filled in. On click, it would need to send an ajax request to the ‘like’ API, and would need to handle any potential error conditions. (e.g. archived topics can’t be liked, you can’t revoke a like after a certain time period, etc.)