[feat] Add benchmark #1977

Seems there are many git library.

• 6.8K https://github.com/isomorphic-git/isomorphic-git
• 5.4K https://github.com/nodegit/nodegit
• 3K https://github.com/steveukx/git-js

I guess each library has its own advantages, but it is not clear the performance of each library compared to raw git command.

Would be nice if these project can add some benchmark on some real world cases, like

https://stackoverflow.com/questions/610208/how-to-retrieve-a-single-file-from-a-specific-revision-in-git