Nvim-tree.lua: Add option to use .gitignore files to ignore paths

[peach-lasagna]

[kyazdani42]

would be great indeed, behind an option because i believe it might impact performance a little

[afonsocarlos]

I can take this

[peach-lasagna]

first

[afonsocarlos]

Haha, didn't know you were developing this already. That's fine, maybe I can help with something else then

[peach-lasagna]

Done. thanks, kyazdani!