Feat: Add theme chooser

Created by: balrajsingh9

Description of PR

Dark theme completely overhauled. Written from scratch and all buggy colors are fixed. Introduces a new way to choose the theme and primary color(thanks to twitter) 👍

• Add 3 background color options - Default, Dim, Lights Out
• Add 6 beautiful primary colors
• Many color fixes(visibility issues) from old dark theme
• Add style improvements and refactor a few components to use primary color.
• Zero delays in render (you can see a small glitch previously when revisiting the page) after applying theme when the page is revisited. Use localStorage to cache the color-combination.

Relevant Issues
Fixes #1417 (closed)

Checklist

• Compiles and passes lint tests
• Properly formatted
• Tested on desktop
• Tested on phone

Screenshots

• Desktop : Chrome, Firefox , Safari

• Mobile Device : Chrome