Add .dropboxignore directory to exclude folders without using selective sync

Megan I'm absolutely livid that you want to gaslight us to tell us this is delivered. Not only does the proposed solution NOT EVEN PREVENT LOCKING AND SCANNING OF IGNORED FILES/FOLDERS (causing tons of errors), it's nowhere near sufficient to our requests. WE HAVE BEEN SCREAMING THIS FOR YEARS AND DESPITE BS RESPONSES AND PROMISES, WE HAVE BEEN DELIVERED NO USABLE SOLUTION. 

This extremely important feature request has been a major inconvenience for a sizable portion of your community for nearly a decade and have been given nothing but insufficient responses despite detailed explanation as to why the proposed solution is not sufficient. This is a DAILY issue for me and it's extremely frustrating how you have ignored all the comments clearly stating how the solution is not sufficient FOR YEARS!!!!! 

If I try to compile a Visual Studio project in dropbox without disabling sync (even with the "obj" folder ignored), files still get locked, causing compilation errors every single time. I primarily use Dropbox to keep an active backup of my coding projects.