Summary:
This allows bundles to have their `.buildignore` file. I did that first to remove some things from the `static` folder, but it turned out that those aren't just unnecessary for the bundle but completely unused in general. I still think there may be a case for allowing this on a per-package basis.
Right now it excludes `.ts` files, license files and readmes. Full list of excluded files is here: P129474747
It adds up to about 6MB in the *DEFLATE compressed* bundle.
Reviewed By: nikoant
Differential Revision: D21176143
fbshipit-source-id: a13e900152617fdf1c2dbfa6330c0a06a75e5484
4d58563168