Restrict which files are packaged

[paulvarache]

Keeping npm modules as light as possible will speed up download times and disk space usage of users.

Adding the files key in package.json will let npm know which files to package. More info here: https://docs.npmjs.com/files/package.json#files

If I missed files required to use this module, please let me know and I will update this PR.

Npm pack results:
Before

npm notice === Tarball Details ===
npm notice name:          resolve
npm notice version:       1.9.0
npm notice filename:      resolve-1.9.0.tgz
npm notice package size:  18.3 kB
npm notice unpacked size: 92.3 kB
npm notice integrity:     sha512-K0N68lfSB1jWh[...]vyd7JamKd1vug==
npm notice total files:   85

After

npm notice === Tarball Details ===
npm notice name:          resolve
npm notice version:       1.9.0
npm notice filename:      resolve-1.9.0.tgz
npm notice package size:  7.4 kB
npm notice unpacked size: 28.6 kB
npm notice shasum:        53bde3e8bcf146287f3003b006190895f0cd10dc
npm notice integrity:     sha512-hnhiX8nZHj87g[...]uYZ2V+XlrYJnA==
npm notice total files:   11

[ljharb]

No thank you. The files property is incredibly dangerous and should never be used; and the size of the installed package is irrelevant. Additionally, npm explore resolve && npm install && npm test should always work (for all modules).

[ljharb]

See not just #82, but #149 (review), #132 (review), #128 (review), #59 (comment),
#164 (comment), #171 (comment)

[paulvarache]

It seems indeed that I'm not the only one questioning this, but that is up to the package maintainer. Thank you for the explanation.

[ljharb]

Unfortunately the npm docs recommending “files” means that many people are unaware of how dangerous it is to use.