We have added a Media Library (file upload widget) for the composer through which you can upload images and videos from your device.
Using a Media Library for Blog Post:
To upload your images and re-use them in the future while composing a blog post:
Navigate to Composer Blog Post section.
Click on the Image Upload Icon.
Once you click on it, a media library will appear on your screen where you can add your images.
P.S We will soon have the integration available with Dropbox, Google Drive, Box and few others.