Add .npmignore

[AaronO]

Reducing npm install size from ~3MB to ~64KB.

This has no negative side effects whatsoever and simply speeds up lunr download.

It's not an essential optimization, but it's small and easy.

[AaronO]

PS: I'm working on adding lunr to gitbook (https://github.com/GitbookIO/gitbook). And I just thought that the install size was a bit excessive and decided to remove some unnecessary cruft.

Let me know if you have any questions

[olivernn]

Thats quite a drop in install size!

I'm actually a bit of a noob with npm, but wouldn't it still be good to have the tests, and potentially the build dir around? I'm just thinking about running npm test etc?

GitBook is really cool project by the way, nice work.

[cvan]

do you need leading slashes?

[KyleAMathews]

Given that people download from NPM over and over and very rarely edit, I'd say it's the right optimization to not include anything but what's necessary and if someone does want to make modifications and run tests, they can do a quick git clone (which they'd need to do anyways to make contributions). I use NPM for both my api and frontend so very much appreciate fast downloads :)