[charts] Add TS definition to the exported elements

[alexfauquette]

I created a basic nextjs with charts to reproduce this issue comment. It failed to build because of missing TS definition.

https://github.com/alexfauquette/charts-next-test

The modification in this PR made directly in the node_module allowed to build

[mui-bot]

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Updated pages

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These are the results for the performance tests:

Test case	Unit	Min	Max	Median	Mean	σ
Filter 100k rows	ms	312.3	496.1	363	377.16	68.229
Sort 100k rows	ms	376.1	798.2	685.2	653.72	153.645
Select 100k rows	ms	127.3	276	215.8	201.18	49.954
Deselect 100k rows	ms	99.7	291.8	205	175	67.523

Generated by 🚫 dangerJS against e99dc1e

[Janpot]

Could work, I'm used to seeing it this way:

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

Never seen that fail, though Typescript seems to discourage the reuse of declaration files for both ESM and CommonJS.

[alexfauquette]

To get it works with nested imports such as @muo/x-charts/LineChart I needed the following diff

  "exports": {
    ".": {
      "types": "./index.d.ts",
      "require": "./index.js",
      "import": "./esm/index.js"
    },
    "./*": {
-      "types": "./*.d.ts",
+      "types": "./*/index.d.ts",
      "require": "./*",
      "import": "./esm/*"
    }
  }

---

If others found this PR the reason is node subpath patterns:

Even if it uses *, the pattern matching does not work like .gitignore config files. The * in ./* can be any string including /.

So for @mui/x-charts/LineChart the ./* will simply do * = LineChart and then look into build/LineChart.d.ts which does not exist. With the modification it will look in build/LineChart/index.d.ts