Improve bundling

[bookmoons]

Bundles a prepackaged compatibility layer. Conversion deploys the new library to the output location. Converted code imports from the library. Shell script bundle can be used by developers to update the compatibility layer.

Adds option --out/-o for specifying output file.

Defines command jmeter-to-k6 to be installed with the package.

Closes #3.

[robingustafsson]

@bookmoons I'm going to test this PR some more tomorrow, see how the k6 memory usage fares. I might re-open and merge this PR and then add an issue about fixing the dynamic generation of jmeter-deps.js in a separate issue, we'll see.

[robingustafsson]

Turns out the memory usage is really high with jmeter-compat.js, I top out at ~2.5 GiB of RAM with 1 VU and a very simple/short script. We're going to look at keeping the deps as separate files as was originally implemented but doing it in such a way as to make the tool publishable and installable via npm.