ignore npm node_modules dirs
ignore npm node_modules dirs

We'd never want to commit these, so just always ignore them.

This creates some redundancy across top/subdirs, but this is because
we mirror out subdirs into dedicated git repos.

Change-Id: I4aff2d37f2f98b23cb86936198a98abc1015a0b6
Reviewed-on: https://chromium-review.googlesource.com/1027063
Reviewed-by: Vitaliy Shipitsyn <6f51537d61e46a00bf958b60dbef5b5870c2bf22@google.com>
Tested-by: Mike Frysinger <8f3f75c74bd5184edcfa6534cab3c13a00a2f794@chromium.org>

chromium/hterm,chromium/hterm,chromium/hterm,chromium/hterm