How do you indent a bulleted list in a README file using GitHub flavored markdown?

I know I can use asterisks to do something like this:

• list item1
• list item2

but I was expecting something like ** to indent it one further. Is it possible?

Sub Lists in GFM(github-flavored-markdown) are done the ways represented below.

- Item 1
- Item 2
- Item 3
  - Sub Item 1
  - Sub Item 2
   
#^ two spaces

OR

* Item 1
* Item 2
* Item 3
  * Sub Item A
  * Sub Item B

Refer to this Cheatsheet