Add exports map with ESM-flavoured type declarations for node16/nodenext

[markedwards]

Problem

Under TypeScript's moduleResolution: node16 / nodenext (the modern default for ESM projects), material-react-table resolves to the wrong type shape.

Two things combine:

1. No exports field. The package ships main (CJS) and module (ESM), but nodenext ignores module, so it falls back to the CJS build.
2. A single dist/index.d.ts. Under node16/nodenext, a .d.ts file is interpreted as CommonJS when the package has no "type": "module" — regardless of which resolution condition reached it. So dist/index.d.ts (correct for the ESM build) is read in a CommonJS context and named imports/types resolve incorrectly.

Fix

Add an exports map with per-condition types, and emit an ESM-flavoured declaration file so ESM consumers get ESM-interpreted types:

"exports": {
  ".": {
    "import":  { "types": "./dist/index.d.mts", "default": "./dist/index.esm.js" },
    "require": { "types": "./dist/index.d.ts",  "default": "./dist/index.js" }
  },
  "./*": "./*"
}

dist/index.d.mts is produced as a second output of the existing rollup-plugin-dts step — the same bundled declarations, just written with the .d.mts extension so it's read as ESM:

{
  input: './dist/types/index.d.ts',
  output: [
    { file: `./${pkg.typings}`, format: 'esm' },   // dist/index.d.ts
    { file: './dist/index.d.mts', format: 'esm' },  // added
  ],
  plugins: [ /* … */ dts() ],
}

No source changes, no new dependencies, no copy step — the declaration bundler emits both files in the same pass.

Backwards compatibility

Additive, no breaking change:

• main, module, typings are retained, so legacy resolvers and bundlers behave exactly as before.
• The require condition still points at the unchanged dist/index.d.ts, so CommonJS consumers are unaffected.
• "./*": "./*" preserves every existing deep import (e.g. material-react-table/locales/...), so the exports map restricts nothing that resolved before.

The only change is that moduleResolution: node16/nodenext consumers now get correct types. Safe as a patch release.

---

The build was not run in this PR. The resulting artifact shape (dist/index.d.mts + the exports map) was validated by applying the equivalent change to an installed 3.2.1 and type-checking a real nodenext consumer — types resolve correctly. The rollup-plugin-dts change is a standard second output writing the same bundled declarations to a .d.mts.

[vercel]

@markedwards is attempting to deploy a commit to the Kevin Vandy OSS Team on Vercel.

A member of the Team first needs to authorize it.