Add Terser as minifier

[Swaagie]

Summary

Add support for Terser minification.

• tests added for separate Config class
• docs added in README.md
• JSDoc inline

Changelog

Added.

Test Plan

Unit test added using Terser, ES6 source code and proper wrhs.toml fixture.

[msluther]

LGTM so far.

[chrisabrams]

What's the advantage of using fingerprinting for hashing the file name vs using Webpack's hashing?

[msluther]

Overall 👍, requesting comments to make sure we have enough debugging information for if/when minification fails.

[msluther]

while we're in here, can we make sure we know when minification is starting/done in status events (and probably which minifier is being used)? and make sure that this error from the minifiers get tagged in status events in such a way that we know they originated from minification (and which minfiier).

[Swaagie]

Good idea, but I'm going to consider this out of scope. https://github.com/godaddy/carpenterd-worker/blob/master/builder.js#L2 workers-factory is only a dependency of carpenterd-worker so I assume we most likely need to either do the work there or give the workers-factory access to the writeStream. I don't consider that to be something we want though. Ideally workers-factory emits events which we can listen to somewhere around here https://github.com/godaddy/carpenterd-worker/blob/master/builder.js#L251-L272 Happy to make a ticket for this though.