fix(pkg): add a default fallback export (#523)

* fix(pkg): add a default fallback export

* docs: add note on needed config changes for TypeScript

Author: wolfy1339

README.md

@@ -66,6 +66,12 @@ Install with `npm install @octokit/oauth-app`
 </tbody>
 </table>
 
+> [!IMPORTANT]
+> As we use [conditional exports](https://nodejs.org/api/packages.html#conditional-exports), you will need to adapt your `tsconfig.json` by setting `"moduleResolution": "node16", "module": "node16"`.
+>
+> See the TypeScript docs on [package.json "exports"](https://www.typescriptlang.org/docs/handbook/modules/reference.html#packagejson-exports).<br>
+> See this [helpful guide on transitioning to ESM](https://gist.github.com/sindresorhus/a39789f98801d908bbc7ff3ecc99d99c) from [@sindresorhus](https://github.com/sindresorhus)
+
 ### For OAuth Apps
 
 ```js

scripts/build.mjs

@@ -67,12 +67,13 @@ async function main() {
       {
         ...pkg,
         files: ["dist-*/**", "bin/**"],
-        main: "./dist-node/index.js",
         types: "./dist-types/index.d.ts",
         exports: {
           ".": {
             types: "./dist-types/index.d.ts",
             import: "./dist-node/index.js",
+            // Tooling currently are having issues with the "exports" field when there is no "default", ex: TypeScript, eslint
+            default: "./dist-node/index.js",
           },
         },
         sideEffects: false,