fix(pack): sort files to produce identical output on Windows and Unix

[merceyz]

Summary

Running yarn pack on Windows and Unix systems produce different results, since on Unix systems the files are sorted while on Windows they aren't.

Running yarn pack on https://github.com/arcanis/babel-plugin-lazy-import produces this output on Windows

$ tar -ztf babel-plugin-lazy-import-v1.0.0.tgz
package
package/index.js
package/package.json
package/README.md

While on Unix it produces

$ tar -ztf babel-plugin-lazy-import-v1.0.0.tgz
package
package/README.md
package/index.js
package/package.json

This PR fixes this by telling tar-fs to sort the files before it packs them. yarn pack also included the .yarnrc.yml config file so I added it to the DEFAULT_IGNORE list.

Test plan

Run yarn pack in a repository containing multiple files and check that the output of tar -ztf package.tgz is the same on Windows and Unix