Adding a project structure diagram to the README or to a new file

[unrealapex]

I think a project structure would be useful for any new contributors who wanted to see how the repo was structured quickly. Here are some examples:

project
|   README.md
|   file001.txt    
|
|---folder1
|   │   file011.txt
|   │   file012.txt
|   │
|   |---subfolder1
|       │   file111.txt
|       │   file112.txt
|       │   ...
|   
|---folder2
     │   file021.txt
     │   file022.txt

https://github.com/UnrealApex/monkeytype/blob/UnrealApex-project-structure/PROJECT_STRUCTURE.md
https://stackoverflow.com/questions/19699059/representing-directory-file-structure-in-markdown-syntax
https://github.com/powerline/powerline/blob/develop/README.rst#configuration