fix(pkg): add main field

Some tools don't play well with only having the `exports` field present.
See octokit/core.js#662

Author: wolfy1339

scripts/build.mjs

@@ -61,6 +61,8 @@ async function main() {
       {
         ...pkg,
         files: ["dist-*/**", "bin/**"],
+        main: "dist-bundle/index.js",
+        types: "dist-types/index.d.ts",
         exports: {
           ".": {
             types: "./dist-types/index.d.ts",