Add node_modules to .gitignore

[MrSuttonmann]

We really don’t want to commit the node_modules folder into the repo, so I’ve added it to the .gitignore file.

[AlexxIT]

There is no node_modules in this project

[MrSuttonmann]

There is a package.json with dev dependencies listed. Running npm install will create a node_modules folder with a large number of files inside. This should not be committed to the repository, hence the PR.