Remove module tag. Now interpreted as CommonJS

[schloerke]

Changes:

• The return TypeScript type for setup() is (void | Promise<void>) (https://github.com/evanw/esbuild/blob/223150f924d746226eedd703d7419dfa636c642f/lib/shared/types.ts#L189). When there are no babel options to parse, it now returns nothing.

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Changes:

• Use require() / modules.export to import objects and export the default value
• Remove "type": "module" from package.json to default back to "type": "commonjs"

External Support:

• From https://redfin.engineering/node-modules-at-war-why-commonjs-and-es-modules-cant-get-along-9617135eeca1

1. Provide a CJS version of your library
   ...
   If your library only provides a default (unnamed) export, you’re done

Since the plugin is small and only has a default export, then we can convert it to a CJS module. Now both CJS and ES modules can require/import this module.

(Motivation by not being able to import ES modules within ts-node.)