Improvement to dark-tweaks, presist dark mode, add transitions, etc

[amitojsingh366]

Below mentioned things are added in this pr:

• persistent color mode (dark, light)
• components using the new color mode system
• smooth transition between colorModes

this was achieved by creating a context provider using the context api called ThemeProvider it can be found at beta/src/modules/ThemeProvider.tsx

[amitojsingh366]

@gaearon this should check a few boxes for your PR #4019

[gaearon]

• The formatting changes make it very difficult to see what's changed in the PR. When you send a PR, please exclude any formatting changes. We use Prettier. It seems like maybe you're also using Prettier but it doesn't respect the project settings? Not sure what happened here.
• I'm not sure I understand what value the transition brings. I don't think it's necessary.
• There is a significant flaw of this solution. That is — the page flashes from white to dark on load. That's not acceptable and is part of the reason why we haven't implemented this yet. I'll take another look but I think I'll need to implement this from scratch because we need to avoid this flaw.

[gaearon]

Hey! Appreciate the effort. We've had to do a bunch of things differently to make it work well with SSR. I already merged the corresponding PRs but thanks for trying!