Yes it is, it just involves adding an html element below it
> Will they get into the business of fact checking everyone over certain number of followers
Their choice, because of the first amendment they can do it to anyone or noone at their leisure or based on whatever criteria they like and as arbitrarily as they like.
> Will they do it impartially world-wide
Their choice, because of the first amendment they can choose to be as impartial or as partial as they like as locally or globally as they like.
> How can they even be impartial world wide given the different contradictory points of view, valid from both sides
The simplest solution is to not be impartial, but that's a decision that is wholly up to them and whatever they decide is protected by the first amendment
See how simple it is? They do whatever they feel like and the government is obligated to not interfere. The end.
(Other governments might object to some of these decisions, the US government most certainly has no legal power to)