switch from XMLHttpRequest to fetch

[oldwizard1010]

fetch works much better with cors stuff

https://github.com/JakeChampion/fetch or https://www.freecodecamp.org/news/create-a-custom-fetch-api-from-xmlhttprequest-2cad1b84f07c

can be used for too old browsers

[svenberkvens]

Looks like a change request for HTMX 2.0 where support for Internet Explorer 11 will be dropped.