Add .dropboxignore directory to exclude folders without using selective sync

This is the top-voted issue by a factor of 3 and there are already existing patterns for how the behaviour can be implemented (e.g. gitignore). Please can we prioritise this feature, it would be a massive help.

I've tried various workarounds but none are really reliable. In all of them, if you create a new folder on one of your machines, or if you get a new device, you have to be careful to remember each of your special cases and set them up, in order to avoid a huge accidental sync. This is also true for the Ignore Files feature - it is really only a workaround for these use-cases, because it's local to the device. A .dropboxignore file is the right solution; the implementation only needs to be local, but because the .dropboxignore file itself is synced, the effect will be across all my devices. Easy and effective.