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