Mild Dark Mode with less contrast

[cprosser]

This pull request adds a new color theme "Mild Dark". I suffer from chronic migraines with light sensitivity and this is much easier to look at. The goal was to mellow out the contrast in all the places I could find, especially large areas.

I'm looking for feedback on any structural changes that might be required. I took color inspiration from text editors I use that have mellow dark themes.

Status

1. Tested on Windows
2. Prefs reading/writing works
3. New element in prefs dialog
4. Keyboard shortcut theme rotation works
5. New menu item
6. Not compiled on MacOS yet (I have an M1 air but haven't configured the dev env.
7. I cloned the existing CSS file from Dark, but didn't change it. I have no idea how to test it (I saw some comment that the html server was no longer maintained?) and don't know if it needs updating.
8. I reused the icons from dark mode, I find the hot pink a little too bright but haven't bother to update them
9. I can't figure out how to change the background fill of the Link and Tap buttons.

Screenshots

Current Dark Mode Overview

Mild Dark Mode Overview

Menu Item

Prefs Panel

Hover Color
Note: the mouse cursor isn't showing here

Selection
Not really thrilled with this, but it works.

[samaaron]

Having a colour theme that is comfortable for those that suffer from migraines is a very good call.

Thank-you so much for this work.

However, the default colour themes for Sonic Pi are part of its identity. I'm wondering if there are tweaks that can be made to a theme like this which are inline with this identity but also fulfil the goal of being easy on the eyes.

Would you be interested in helping find such a compromise - using this work as a starting point? I was already thinking of an orange-rather-thank-deep-pink-based theme - would this work for you?

[cprosser]

@samaaron I'm absolutely open to work on this theme to match the spirit of your original ones. I tried my best to steal mellow colors in the spirit of the existing Sonic Pi themes, but I was focused on getting a prototype done before I had to go back to work that was good enough so I could work on my sculpture without having to squint.

Where's the best place to carry on that conversation? I can't promise to be fast, I get a couple of hours each weekend, but tweaking colors doesn't take too long.

[samaaron]

Sounds great. How about I merge this as it stands then start tweaking with the colours - checking with you to see if my choices are suitable. Hopefully after enough iteration we can arrive at something that works all round!

[rsmath]

Is this ready to be used now?