fix: avoid CJS interop issue

Some compilers transpile `import plugin from "package";` into `var plugin = require("package");`,
not `var plugin = require("package").default;`.
(Maybe this is a bug of the compiler.)

Currently `export default plugin;` is transpiled to `module.exports.default = plugin;`,
but this does not work for the above case.
It will work if `export default plugin;` is transpiled to `module.export = plugin;`,
but in this case `var plugin = require("package").default;` will not work.

Adding `export { rules, configs };` will allow the both cases to work,
without breaking compatibility.

src/index.ts

@@ -8,3 +8,4 @@ const plugin = {
 } satisfies ESLint.Plugin;
 
 export default plugin;
+export { rules, configs };