convert given file to data URL
$ go install github.com/abiriadev/dataurl@latest$ dataurl ./image.png data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABAQMAAAAl21bKAAAAA1BMVEUAAACnej3aAAAAAXRSTlMAQObYZgAAAApJREFUCNdjYAAAAAIAAeIhvDMAAAAASUVORK5C$ dataurl ./post.md data:text/markdown; charset=utf-8;base64,IyBIZWxsbywgd29ybGQh $ dataurl --mime 'text/plain; charset=UTF-8' ./post.md data:text/plain; charset=UTF-8;base64,IyBIZWxsbywgd29ybGQh$ dataurl < ./post.md data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABAQMAAAAl21bKAAAAA1BMVEUAAACnej3aAAAAAXRSTlMAQObYZgAAAApJREFUCNdjYAAAAAIAAeIhvDMAAAAASUVORK5C $ dataurl --mime 'text/plain; charset=UTF-8' ./post.md data:text/plain; charset=UTF-8;base64,IyBIZWxsbywgd29ybGQh