fix: path imports for typescript (#493)

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

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

**Describe the solution you've chosen**

Remove export block to support node 10 and allow internal to be imported

**Describe alternatives you've considered**

Linking `internal.ts` in `main.ts`, however we look to want to keep
these seperate

**Checklist**

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- [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] Passed `npm run test:publish`
- [x] Tested change with `npm link @netlify/functions`

internal.d.ts

@@ -0,0 +1,2 @@
+// eslint-disable-next-line import/extensions
+export * from './dist/internal.js'

package.json

@@ -1,16 +1,27 @@
 {
   "name": "@netlify/functions",
   "main": "./dist/main.js",
-  "types": "./dist/main.d.ts",
   "type": "commonjs",
   "exports": {
     ".": {
-      "import": "./dist/main.mjs",
-      "require": "./dist/main.js"
+      "require": {
+        "types": "./dist/main.d.ts",
+        "default": "./dist/main.js"
+      },
+      "import": {
+        "types": "./dist/main.d.mts",
+        "default": "./dist/main.mjs"
+      }
     },
     "./internal": {
-      "import": "./dist/internal.mjs",
-      "require": "./dist/internal.js"
+      "require": {
+        "types": "./dist/internal.d.ts",
+        "default": "./dist/internal.js"
+      },
+      "import": {
+        "types": "./dist/internal.d.mts",
+        "default": "./dist/internal.mjs"
+      }
     }
   },
   "version": "2.6.1",
@@ -19,7 +30,8 @@
     "dist/**/*.js",
     "dist/**/*.mjs",
     "dist/**/*.d.ts",
-    "dist/**/*.d.mts"
+    "dist/**/*.d.mts",
+    "internal.d.ts"
   ],
   "scripts": {
     "build": "tsup src --format esm,cjs --dts --clean",