I have just copied parts of this sheet because the entire sheet is very long and you can access it HERE. There is a version available for Mac users as well. To find the Mac shortcuts, you will have to scroll down in the link I posted earlier till the end of the page.
Going through these shortcuts, I found that some of them work on any other web tools and not just Google Docs like, for instance, the combinations of keys to copy, paste, select..etc but some of them are limited to only Google Docs.
Pleas have a look and share with us what you think of it . Enjoy