RFC: Define preProcessors API

[julian-londono]

So far added an initial set of thoughts regarding this API. Will delve more concretely into the actual pre-processors loader set up/syntax after this set of initial thoughts for resourceProviders, preProcessors, and postProcessors

[julian-londono]

Update: Working on defining what a preProcessor loader itself will look like and behave like this afternoon

[julian-londono]

Please note I've added some initial thoughts on what a preprocessor could look like as well as a tweak to the API.md design doc

[julian-londono]

To anyone here to review/comment, thank you. The crux of the idea is here: Implementation of Loader Workflow for On-the-Fly Running (api/EXPLORATION.md).

You can find the main loader here: src/loader.mjs

The API for preProcessors (converting from one format to some form of JS) is here: api/API.md

Finally, a I have 2 working loaders so far:

• a preProcessor that converts from YAML to JSON
• a postProcessor that adds appends a simple console.log("blah") to the end of any module

To run this prototype:
node --experimental-top-level-await --experimental-loader ./src/loader.mjs ./examples/loaders/test.mjs

[julian-londono]

Acknowledging the further conversation that has to happen regarding esm: Modify getFormat and getSource loader hooks #34144, I've decided to have preProcessors wrap their output in modules with default exports. I've included an example on how this could work with the current YAML loader.