build: add exports field to package.json

BREAKING CHANGE
See https://nodejs.org/api/packages.html#packages_package_entry_points

Author: ahnpnl

package.json

@@ -3,6 +3,12 @@
   "version": "27.0.0-next.9",
   "main": "dist/index.js",
   "types": "dist/index.d.ts",
+  "exports": {
+     ".": "./dist/index.js",
+     "./presets": "./jest-preset.js",
+     "./utils": "./utils/index.js",
+     "./package.json": "./package.json"
+   },
   "bin": {
     "ts-jest": "cli.js"
   },