`compileNamespace` should take package.json "type" into account

Nobody has claimed this yet.

When you set `"type": "module"` in your JSON both `.js` and `.ts` files (if you are using TypeScript) are considered modules. You only need to use the `.m[jt]s` or `.c[jt]s` extensions as an override.

I bring this up because it also applies to TypeScript, not just vanilla JavaScript. And both can have `module.exports =` or `export const` depending on the combination of package type and extension used.

I'm running into issues with babel when compiling code with a mix of `.ts` and `.cts` extensions. Babel just compiles everything to `.js`. There doesn't seem to be a way to solve this.

Also, newer node versions unfortunately are extremely strict about this, so if you don't use the right syntax it just fails.

I would like to propose reading the package.json type and use the following logic:

- If module and `compileNamespace` is `"cjs"`, write `module.exports =` to a `.cjs` file
- If module and `compileNamespace` is `"es"`, write `export const messages =` to a `.js` file
- If module and `compileNamespace` is `"ts"`, write `export const messages: AllMessages =` to a `.ts` file
- If commonjs and `compileNamespace` is `"cjs"`, write `module.exports =` to a `.js` file
- If commonjs and `compileNamespace` is `"es"`, write `export const messages =` to a `.mjs` file
- If commonjs and `compileNamespace` is `"ts"`, write `export const messages: AllMessages =` to a `.mts` file

If this is too complicated I understand. Ideally Lingui would just have a "typescript" option and just detect the package.json type. And optionally be able to provide a custom compilation function.

Start by locating the compileNamespace implementation and any tests covering generated JavaScript or TypeScript output. Read how package.json is currently handled, then verify the module/commonjs and cjs, es, and ts combinations described in the issue, including the expected output extensions and syntax.

Written by the indexing model from the issue text.