chore: clean up native typings

Author: kevinmichaelchen

native.d.ts

@@ -0,0 +1,4 @@
+export declare class CelProgram {
+  static compile(source: string): Promise<CelProgram>;
+  execute(context: Record<string, any>): Promise<any>;
+}

package.json

@@ -8,7 +8,8 @@
       "types": "./dist/src/index.d.ts"
     },
     "./native": {
-      "import": "./index.js"
+      "import": "./index.js",
+      "types": "./native.d.ts"
     }
   },
   "types": "./dist/src/index.d.ts",