Vim: bind <tab> to toggle folds
Vim: bind <tab> to toggle folds

In 5f4e5d23f I gave up my beloved `<space>` binding that I used to use
to toggle folds quickly.

Reading this Reddit post gave me the idea to use `<tab>` instead, which
I effectively never use in normal mode, so it's available:

https://www.reddit.com/r/vim/comments/451q7x

Yay.

wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent