This PR fixes the editor colors in dark mode. It bothered me enough to finally fix it :)
The implementation is probably only "good enough" as we'll replace the editor anyway in the future.
Co-authored-by: kolaente <k@knt.li>
Reviewed-on: https://kolaente.dev/vikunja/frontend/pulls/1338
Co-authored-by: konrad <k@knt.li>
Co-committed-by: konrad <k@knt.li>