Possibly there could be a default bank of compression algorithms. Gzip is a good one (as it's tested), but adding others could be useful.
Possible ways to call squish could be:
squish(['gzip', 'deflate', 'lzma'])
or for all of them:
An array or strings would mean use all provided compression algorithms. Empty arguments would mean use all available compression algorithms. Algorithms should be lazy-loaded and throw an exception if they're not there "ONLY IF" they were provided in the array of strings.
This way the user could just npm install/uninstall modules and not have to change the parameters to squish. This would make it much more dynamic and easy-to-use.