This is the mirror image of #2170.

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Add `default_converter` argument to `to_js` and `toJs`. This is the mirror image of #2170.

### Checklists

<!-- Note on checklists:
     If you think some of these steps are not necessary for your PR,
     just remove those checkboxes, or mark them as checked. Otherwise,
     if some checkboxes are left unmarked, we might assume that your PR
     is not ready to be merged and we might keep you waiting -->

- [x] Add a [CHANGELOG](https://github.com/pyodide/pyodide/blob/main/docs/project/changelog.md) entry
- [x] Add / update tests
- [x] Add new / update outdated documentation

#ifndef JS2PYTHON_H
#define JS2PYTHON_H

/**
 * Translate JavaScript objects to Python objects.
 */
#define PY_SSIZE_T_CLEAN
#include "Python.h"
#include "hiwire.h"

/** Convert a JavaScript object to a Python object.
 *  \param x The JavaScript object.
 *  \return The Python object. New reference. If NULL, a Python exception
 *    occurred during the conversion, and the Python exception API should be
 *    used to obtain the exception.
 */
PyObject*
js2python(JsRef x);

PyObject*
js2python_convert(JsRef x, int depth, JsRef defaultConverter);

/** Initialize any global variables used by this module. */
int
js2python_init();

#endif /* JS2PYTHON_H */

#ifndef JS2PYTHON_H
#define JS2PYTHON_H

/**
 * Translate JavaScript objects to Python objects.
 */
#define PY_SSIZE_T_CLEAN
#include "Python.h"
#include "hiwire.h"

/** Convert a JavaScript object to a Python object.
 *  \param x The JavaScript object.
 *  \return The Python object. New reference. If NULL, a Python exception
 *    occurred during the conversion, and the Python exception API should be
 *    used to obtain the exception.
 */
PyObject*
js2python(JsRef x);

PyObject*
js2python_convert(JsRef x, int depth, JsRef defaultConverter);

/** Initialize any global variables used by this module. */
int
js2python_init();

#endif /* JS2PYTHON_H */
