Tech: do not generate ESM dist for preset files

[ndelangen]

Closes #21316

What I did

When TSup is bundling code, it will add a bit of require polyfill code to the output, when it encounters code referencing require in 1 of the entrypoints.

It will add the polyfill code to all entrypoints, and will refuse to treeshake it out.

So I made en excemption for preset entries, to never get a mjs file generated, because those often have references to require in them.

How to test

Run the build process and check for existence of this type of code in dist:

var __require = /* @__PURE__ */ ((x) => typeof require !== "undefined" ? require : typeof Proxy !== "undefined" ? new Proxy(x, {
  get: (a, b) => (typeof require !== "undefined" ? require : a)[b]
}) : x)(function(x) {
  if (typeof require !== "undefined")
    return require.apply(this, arguments);
  throw new Error('Dynamic require of "' + x + '" is not supported');
});

export {
  __require
};

At least within the docs addon this no longer happens.

This code does impact all monorepo packages though, but I think that's fine. AFAIK we never use mjs exports of presets, always the cjs files.

Some day we'll convert everything over to ONLY ESM, and have all packages be type=module, but that's a project for future me.

[ndelangen]

before:

after:

[tmeasday]

Seems like a neat solution