Task lists in all markdown documents

Task lists in issues, comments, and pull request descriptions are incredibly useful for project coordination and keeping track of important items. Starting today, we are adding read-only task lists to all Markdown documents in repositories and wikis. So now, when you write:

### Solar System Exploration, 1950s – 1960s

- [ ] Mercury
- [x] Venus
- [x] Earth (Orbit/Moon)
- [x] Mars
- [ ] Jupiter
- [ ] Saturn
- [ ] Uranus
- [ ] Neptune
- [ ] Comet Haley

It will render like this, everywhere on GitHub:

Edit the document or wiki page and use the - [ ] and - [x] syntax to update your task list.