Some small fix and Trello Discussion Suggestion

@ymichael, this pull request contains the following:

1. In README.md, the instruction for setting up the outline-md points to the wrong package
2. Some small typo fix
3. Add a link to ProjectIntern Trello 

Reason for ProjectIntern Trello: 
+ currently there is a **Interview Question PlayGround** board for everyone to discuss and share interview questions they feel interested. 
+ In future, we can add more boards for ProjectIntern internal discussion and other public tasks

Wish my suggestions will contribute to the ProjectIntern project.

Thank you very much.

Best Regards,
GaoXiang