Add /vendor/node_modules to gitignore
Add /vendor/node_modules to gitignore

`node_modules` includes Node.js package files. Application repository
should not store them.

gauravtiwari/webpacker,Davidzhu001/webpacker,usertesting/webpacker,rails/webpacker,rossta/webpacker,shakacode/webpacker_lite,usertesting/webpacker,gauravtiwari/webpacker,rossta/webpacker,rossta/webpacker,usertesting/webpacker,rmckayfleming/webpacker,gauravtiwari/webpacker,rmckayfleming/webpacker,rossta/webpacker,nickpith/webpacker,nickpith/webpacker,nickpith/webpacker,rmckayfleming/webpacker,Davidzhu001/webpacker,Davidzhu001/webpacker,rails/webpacker