[IMP] tooling: add another d.ts file

package.json

@@ -5,7 +5,7 @@
   "main": "dist/owl.cjs.js",
   "browser": "dist/owl.iife.js",
   "module": "dist/owl.es.js",
-  "types": "dist/types/index.d.ts",
+  "types": "dist/types/owl.d.ts",
   "files": [
     "dist"
   ],
@@ -55,6 +55,7 @@
     "npm-run-all": "^4.1.5",
     "prettier": "2.4.1",
     "rollup": "^2.56.3",
+    "rollup-plugin-dts": "^4.2.2",
     "rollup-plugin-terser": "^7.0.2",
     "rollup-plugin-typescript2": "^0.31.1",
     "sass": "^1.16.1",