Make an example on how to serialize/extract correctly Lists

[serban-mihai]

It would be nice to have examples of working with any List<T> or Data types.
Right now I don't understand how to correctly assign values to List keys from the generated schema.

The only way I've been able to work with Lists has been to use _private methods

const message = new capnp.
const requestData = message.initRoot(RequestData);

const headers = requestData._initHeaders(parsedHeaders.length);

parsedHeaders.forEach(({ key, value }, i) => {
  const h = headers.get(i);
  h.key = key;
  h.value = value;
});

But trying the following leads to errors both from typescripts due to type mismatch and also at runtime TypeError: Cannot read properties of undefined (reading 'isWordZero'):

requestData.headers = parsedHeaders.map(({ key, value }) => {
  return { key, value };
});

Also, how to deserialize string each values from the List of structs?