Allows callers to specify a `maxAge` when setting a cookie with the Cookie Store API. Cookie expiry time is already configurable using the `expires` attribute, but `maxAge` provides a more idiomatic option and aligns the Cookie Store API with the options provided by `document.cookie` and the `Set-Cookie` HTTP Header.
Currently, developers can use the `expires` attribute when setting a cookie with the Cookie Store API to set an absolute timestamp for expiry. This can be unintuitive and is impacted by client-side clock skew. RFC6265bis and the document.cookie API provide a `Max-Age` attribute, which allows for relative cookie lifetimes and ergonomic deletion. We should provide a `maxAge` option in the Cookie Store API to support relative expiry and align with these APIs.