Possible to add an env variable like SLIDES_THEME to set Chroma theme for syntax highlight

[chopfitzroy]

Is your feature request related to a problem? Please describe.

Similar to NAP_THEME from Nap I was wondering if we could have something like SLIDES_THEME to set the Chroma theme.

(I am assuming Chroma is being used based on this commit please correct me if I am wrong).

Describe the solution you'd like

Being able to set a SLIDES_THEME environment variable that will update the syntax highlighter used for code blocks in Slides.

Describe alternatives you've considered

Leaving it as is or trying to change the code myself and recompile locally.

Additional context

No other context I can think of.