chore: add "main" to package.json to fix eslint issues (#356)

Author: vimalloc

vite-plugin-ruby/package.json

@@ -3,6 +3,7 @@
   "description": "Convention over configuration for using Vite in Ruby apps",
   "version": "3.2.1",
   "type": "module",
+  "main": "./dist/index.js",
   "types": "dist/index.d.ts",
   "exports": {
     ".": {