chore: export package.json for higher version Node.js (#103)

shikijs/shiki#640

Co-authored-by: Anthony Fu <anthonyfu117@hotmail.com>

package.json

@@ -16,7 +16,8 @@
   "keywords": [],
   "sideEffects": false,
   "exports": {
-    ".": "./dist/index.mjs"
+    ".": "./dist/index.mjs",
+    "./package.json": "./package.json"
   },
   "main": "./dist/index.mjs",
   "module": "./dist/index.mjs",