[Feature Request] Bullets for TODOs

I want to suggest something like this:

Suppose we have ('*' represents unicode bullet from this package):

```
* Heading 1
* Heading 2
```

Now, setting a `TODO` on a heading should result in:

```
☐ Heading 1 # TODO, using a unicode "ballot box"
☑ Heading 2 # DONE, using a unicode "ballot box with check"
```
