Add option to set request mode for fetch API

[andreasa-winenet]

Motivation

It is not strictly necessary in most cases, but if I know I only use URLs from the same-origin it can be better to use mode: 'same-security' for fetch requests to block cross origin requests altogether.

It isn't strictly necessary but it could be used to avoid accidentally calling CORS URLs

Implementation

In https://github.com/mapbox/mapbox-gl-js/blob/v3.24.0/src/util/ajax.ts#L118 add an option to also provide mode similar to cache mode etc.

See also https://developer.mozilla.org/en-US/docs/Web/API/Request/mode and https://developer.mozilla.org/en-US/docs/Web/API/RequestInit#mode

[andreasa-winenet]

ah sorry, I see this should be possible using transformRequest

[andreasa-winenet]

Ah. Sorry, no I was right. I can register the request transformer but the mode parameter is not available in the type and not used in https://github.com/mapbox/mapbox-gl-js/blob/v3.24.0/src/util/ajax.ts#L118