Dark mode

[neilvanbeinum]

This is a 🙋 feature or enhancement.

Summary

Adds a dark mode to the Bridgetown website.

Context

Closes #555

This implementation mainly reuses existing colors. An exception is made for meeting color contrast accessibility requirements though - see inline PR comment.

The styling will of course need various changes to match an actual design but this should hopefully form a basis.

Code syntax styling may be an area that needs extra attention.

Screenshots

Light Mode	Dark Mode

[jaredcwhite]

@vvveebs This is fantastic! And going the extra mile to add the theme picker too. 👍🏻👍🏻

I'll review in more detail soon…would be awesome to roll this out along with Bridgetown 1.2.

[andrewmcodes]

@vvveebs this is looking awesome! I really only found one issue and then there are a few things I want to get your thoughts on:

1. The edge site banner appears to be the wrong color
   

2. The theme picker is excellent but it's a little weird that it doesn't match the style of the rest of the buttons. I think it's ok but one thing I think we should change is that the hover color is blue but it would be nice if it matched the hover color of the dropdown items aka the bridgetown green. Wdyt?

3. These buttons may look better without a border or with different shade of green for the border as opposed to white. Wdyt?
   

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2 & 3 are opinions so not a requirement to merge. Overall I think this look great, thank you so much for the contribution 👏

[neilvanbeinum]

@andrewmcodes thanks for the review! All good points. Responded to them in order:

1. Edge site banner in dark mode updated.

2. It's funny - I didn't even realise this button was so different - guess I'd been staring at it for a while and it became a blind spot! Updated.

themepickerbutton.mov

3. After chat with Jared it seems like we want to go ahead with the border. But I agree straight up white is too much. Updated to a light green.

[jaredcwhite]

@vvveebs Looking gooood 🤩

[jaredcwhite]

@vvveebs I see some room for further tweaking, but I think it'll be better to reason about in followup issues/PRs. Going to go ahead and merge! Thanks again for this fabulous effort!