fix: main path imports for typescript (#495)

**Which problem is this pull request solving?**

Release failures:

https://github.com/netlify/functions/actions/runs/8942002569/job/24563622237

https://github.com/netlify/functions/actions/runs/8939586357/job/24555907790

**List other issues or pull requests related to this problem**

See #491,
#492,
#493

**Checklist**

Please add a `x` inside each checkbox:

- [x] I have read the [contribution
guidelines](../blob/master/CONTRIBUTING.md).
- [x] The status checks are successful (continuous integration). Those
can be seen below.
- [x] Ran `npm run test` which includes `test:publish` and `test:dev`
- [x] Tested with `npm link @netlify/functions`

package.json

@@ -1,6 +1,7 @@
 {
   "name": "@netlify/functions",
   "main": "./dist/main.js",
+  "types": "./dist/main.d.ts",
   "type": "commonjs",
   "exports": {
     ".": {