update focus JS

[Anubarak]

Do not trigger the close handler if the event current target is something different than the actual target to prevent closing on click on something in the focus.

Didn't want to install gulp, I only use webpack with yarn or npm so I didn't create a build for it

[Cam]

@Anubarak looks good.

I'm considering removing build packs anyway. There's no need for them for a simple project like this. I'll start that process then merge this 👍