Fix module resolution

[TimJentzsch]

Description:

When running npm run dev, everything worked fine.
But with npm run build && npm run start, we got the following error:

Error [ERR_MODULE_NOT_FOUND]: Cannot find module '/app/dist/src/logger' imported from /app/dist/src/_main.js
    at finalizeResolution (node:internal/modules/esm/resolve:264:11)
    at moduleResolve (node:internal/modules/esm/resolve:917:10)
    at defaultResolve (node:internal/modules/esm/resolve:1130:11)
    at ModuleLoader.defaultResolve (node:internal/modules/esm/loader:396:12)
    at ModuleLoader.resolve (node:internal/modules/esm/loader:365:25)
    at ModuleLoader.getModuleJob (node:internal/modules/esm/loader:240:38)
    at ModuleWrap.<anonymous> (node:internal/modules/esm/module_job:85:39)
    at link (node:internal/modules/esm/module_job:84:36) {
  code: 'ERR_MODULE_NOT_FOUND',
  url: 'file:///app/dist/src/logger'
}

This is because the --experimental-specifier-resolution=node flag got removed in nodejs/node#44859.
Instead, we now use the commonjs-extension-resolution-loader custom loader and specify it with the --loader flag.

See also https://github.com/orgs/nodejs/discussions/46298#discussioncomment-4744722.

Checklist:

• Tested the bot on both clients with a few commands
• Updated the README if necessary
• Updated the version string in the package.json if necessary