Rainbow brackets for Positron

[tacaro]

This was one of my favorite 'quality of life' improvements in newer Rstudio versions. It'd be wonderful if this could be integrated. Current Rainbow Bracket VSCode extensions do not transfer to Quarto's visual mode (though they do work in source mode!).

[testlabauto]

Hi! Thank you for your feedback, @tacaro !

I have opened this enhancement to triage and track this request: #8026