fix: TypeScript 6 defaults module to "esnext"

[koglerch13]

TypeScript 6 changed the default module to "esnext" (previously it was CommonJS) - reference: https://devblogs.microsoft.com/typescript/announcing-typescript-6-0/

In our setup, we imported another file in our /en/index.ts file:

import en from './en';
export default en;

after upgrading to TypeScript 6, generating the language files failed.
More details can be found in the corresponding issue: #789

The fix sets the module option to use CommonJS (which was used implicitly before anyway).

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Tests

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generator

If you change something in the generator, please also:

• add some snapshot tests to the packages/generator/test/generator.test.ts-file
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• then add all the created *.expected.*-files to the git-index and
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