Reexport eslint bin in @mailpoet/eslint-config explicitly

We're using @mailpoet/eslint-config to share eslint itself so it's
correct to reexport the executable that's being used. This also makes
the command work in the premium plugin without need to address the
".bin" paths within "node_modules".

[MAILPOET-5015]

packages/js/eslint-config/package.json

@@ -4,6 +4,9 @@
   "version": "0.1.0",
   "description": "",
   "main": "index.js",
+  "bin": {
+    "eslint": "./node_modules/eslint/bin/eslint.js"
+  },
   "scripts": {},
   "devDependencies": {
     "@babel/eslint-parser": "^7.21.3",