Icons, bold, italics?

Seems like it isn't supported it would be nice to render icons as well as bold and italic text. I usually use representative icons to quickly visualize similar to important info. Bold to call attention to a phrase, and italic to denote a "comment".

Like this

```markdown
# Header

- ![alt text][shield] some important note
- some **bolded** note
- *interesting fact*

[shield]: https://github.com/adam-p/markdown-here/raw/master/src/common/images/icon48.png "shield"
```