[FEATURE] icon for npm-shrinkwrap.json

[jkowalleck]

npm knows multiple lock file formats, besides package-lock.json.
see https://docs.npmjs.com/cli/v8/configuring-npm/npm-shrinkwrap-json

the icon theme already puts a proper icon for package-lock.json.
but npm-shrinkwrap.json is detected as arbitrary json file.

request: npm-shrinkwrap.json has the same icon as the current package-lock.json has

[jkowalleck]

as a matter of documentation, the shrinkwrap was added to atom-file-icons icons via 1.7.16
but it might be broken in the current versions.

nevertheless, please have this feature/fix for VSCode