Also export editor converter Node APIs

[JoshuaKGoldberg]

🚀 Feature Request

Following #732 to add a Node API and #820 to add a standalone comment conversion API, it might also be useful for Node API consumers to be able to convert their editor configuration file(s) automatically.

Existing Behavior

The convertEditorConfig(s) methods are not exported as a standalone function via the Node API.

Change Proposal

Export standalone equivalent(s) to those methods so that someone could call them to convert their editor configuration(s) without tslint-to-eslint-config using its own file I/O.

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~@JamesHenry, do you predict wanting to use this as part of the angular-eslint schematic (https://github.com/angular-eslint/angular-eslint/pull/173)? If so, I can tackle this pretty quickly alongside #820. If not, this would be a good contribution opportunity for someone new to tackle if they're interested.~ This isn't necessary for the angular-eslint schematics. Which makes it a perfect good first issue for someone who'd like to try adding to tslint-to-eslint-config without time pressure! ✨