While it's nice to have another way to use Live Photos, Twitter's a touch behind the curve here. Apple introduced Live Photos on iPhone 6s in 2015. That same year, Tumblr and Facebook started allowing people to share them on their platforms, while Google's iOS app has been able to convert them into GIFs since 2016. In 2017, Apple offered a way to embed Live Photos on any website.
Twitter's useful Live Photos feature arrives alongside other changes to how it handles images. It'll also preserve JPEG encoding on photos of up to 16 megapixels you upload via the web, instead of transcoding them (which impacts image quality).