[meta] add sideEffects flag

Author: ljharb

package.json

@@ -3,11 +3,11 @@
 	"version": "1.0.1",
 	"description": "Which kind of Collection (Map, Set, WeakMap, WeakSet) is this JavaScript value? Works cross-realm, without `instanceof`, and despite Symbol.toStringTag.",
 	"main": "index.js",
-	"type": "commonjs",
 	"exports": {
 		".": "./index.js",
 		"./package.json": "./package.json"
 	},
+	"sideEffects": false,
 	"scripts": {
 		"prepack": "npmignore --auto --commentLines=autogenerated",
 		"prepublishOnly": "safe-publish-latest",