markdown check list code example

Example 1: checklist github readme

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

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

Example 2: markdown list

1. First item
2. Second item
3. Third item
    - Indented item
    - Indented item
4. Fourth item