Allow custom active search background colour

[marcusmichaels]

Hey folks 👋 – I'm hoping this is in the right area as it's a config/setting, but also related to theming.

I was really happy when search.match_background was shipped as it allowed me to properly see matches, however, it doesn't allow for the active match's highlight colour, and that still looks invisible on some themes such as SynthWave 84 Dark:

"theme": {
  "mode": "system",
  "light": "SynthWave 84 Dark",
  "dark": "One Dark"
}

Adding this helped to add some contrast to the search:

"experimental.theme_overrides": {
  "search.match_background": "#ff00f090"
}

But when cycling through each search the highlight essentially disappears due to lack of contrast (second Test is the active highlight):

I've searched the docs and can't seem to find anything that indicates that this is currently customisable (I would love to be proved wrong here!) so I'd like to raise this as a potential enhancement.