Add support for rainbow colors

[amarakon]

There are plugins that make parentheses rainbow colored (meaning each pair is a different color). The one I use is nvim-ts-rainbow. I think nord-vim should set the default rainbow colors for plugins like nvim-ts-rainbow to use so that users don't have to set it on their own. The colors I chose are red, orange, green, blue, darker blue, purple from the Nord theme. If the colors are not perfect, feel free to change them.

[jvoisin]

Please wrap this in a if has('nvim') condition :)

[amarakon]

Please wrap this in a if has('nvim') condition :)

I did so in the latest commit for this pull request. Thanks.

[svengreb]

Thank you for your patience! 🙏🏼
It‘s been a while since I had free time to focus more on Nord, and my open source projects in general, and invest time in this issue due to work-life balance.

I recently published the first “Northern Post — The state and roadmap of Nord“ announcement which includes all details about the plans and future of the Nord project, including the goal of catching up with the backlog. This issue is part of the backlog and therefore I want to triage and process it to get one step closer to a “clean state“. Read the announcement about reaching the “clean“ contribution triage state in Nord‘s discussions for more details about the goal.

Therefore it has been added for triage in the central and single-source-of-truth project board that is also described in more detail in the roadmap announcement.

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@amarakon Thanks for your contribution 🚀
The pull request has been added for triage and the review will be planned for the next iterations!