Able to upvote links

[WilliamDASILVA]

As a registered & logged-in user, you can upvote links in the "links" view.
This action should be made through a "like" button near each link in the links view.

What's needed:

• Make links "likeable" using the current polymorphic relationship, like the tasks.
• Make a coherent design to integrate a "like" button in the "link" component.
• Update the "link" component to be able to show the "likes" count for each link.
• This would need to update the GraphQL "Link" type to includes the likes.
• Find a way to identify if the currently logged-in user has already liked a link and therefore show a different state in the "link" component.