Custom ExpressJS integration not working

Hey guys,

thanks for the effort of supporting web frameworks so far!

I'm trying to integrate the web framework support into [my SvelteKit adapter](https://www.npmjs.com/package/sveltekit-adapter-firebase), but I'm hitting a dead end.

My project looks like this:
`package.json`:
```
{
"name": "test-app",
"version": "0.0.1",
"type": "module",
"dependencies": {
"@neoconfetti/svelte": "^1.0.0",
"firebase": "^9.13.0",
"firebase-admin": "^11.0.4"
},
"main": ".firebase/functions/render.js",
"directories": {
"serve": "."
},
"files": [
"*",
"**/*"
],
"scripts": {
"build": "echo \"No build needed\""
}
}
```
`.firebase/functions/render.js`:
```
import { init } from './../function.js';

export const handle = init(...);
```
Where init(...) returns a express `(req,res) => void` handler function.

`firebase.json` which lies next to the `dist` folder pictured above:
```
{
"hosting": {
"source": "dist/apps/test-app",
"cleanUrls": true
}
}
```

I'm trying to preview the app with `emulators:start` but my function is not recognized i.e. not showing up in the console output.

I've debugged the `firebase-tools/frameworks` library a bit and it looks like the `getBootstrapScript` function in `firebase-tools/frameworks/express/index.js` is called with the project root (where my package.json lies) which can not be imported. I think it should probably try to import my `render.js` file, but I'm not sure how the framework support works internally.

Is there something wrong with my setup? Is the approach of prebuilding everything even feasible?

Thanks in advance