[git] Add `node_modules` to `gitignore`
[git] Add `node_modules` to `gitignore`

Addition made because some people don't add the `node_modules`
directory in the `.gitignore` file from their repositories.

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

See also: https://docs.npmjs.com/misc/faq#should-i-check-my-node-modules-folder-into-git

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