change/API! ~ add package 'exports' to publicize ESM support

- reveals ESM wrapper providing ESM support (as suggested in "Node Modules at War")

* ref: [Node Modules at War](https://redfin.engineering/node-modules-at-war-why-commonjs-and-es-modules-cant-get-along-9617135eeca1) @@ <https://archive.is/zl0qg>
* ref: [yargs ~ 'Road to ESM/Deno'](yargs/yargs#1706).

package.json

@@ -21,7 +21,19 @@
 	],
 	"type": "commonjs",
 	"main": "./dist/cjs/index.js",
+	"module": "./dist/cjs/esm-wrapper/index.js",
 	"types": "./dist/types/index.d.ts",
+	"exports": {
+		"./package.json": "./package.json",
+		".": [
+			{
+				"import": "./dist/cjs/esm-wrapper/index.js",
+				"require": "./dist/cjs/index.js",
+				"types": "./dist/types/index.d.ts"
+			},
+			"./dist/cjs/index.js"
+		]
+	},
 	"keywords": [
 		"base",
 		"cache",