Improve/fix applying babel to the transformer

[fkling]

Note: If you have problems running codemods and get Babel related errors, run jscodeshift with --no-babel.

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The last change to src/Worker.js causes issues with babel-register. Passing module identifiers causes babel-register to look up those modules in the wrong places. Those modules should be required instead.

Furthermore, we probably don't want to transpile most of ES2015 features since people probably use a Node version that supports those. present-env already supports this:

If you want to compile against the current node version, you can specify "node": true or "node": "current", which would be the same as "node": process.versions.node.

https://babeljs.io/docs/en/babel-preset-env#targetsnode

but we should also include/exclude plugins based on the current node version.

[brieb]

Thank you for fixing this. So sorry for introducing this issue. Will keep this in mind for future reference. TIL.

Should we also add /\/node_modules\// to this ignore list?
cb92c48#diff-e957a0672425b8dcfdcfe9f8cccf36f7