Improve syntax highlighting

[samrap]

In response to #2 and #3 , the syntax highlighting can definitely use some improvement, specifically in JavaScript and Markdown.

The goal of this issue is to clean up/improve the syntax highlighting while maintaining the synthwave aesthetic and avoiding making the theme too colorful.

By version 0.3.0, the goal is to have full support for the following languages:

• Ruby
• Python
• PHP
• JavaScript
• HTML
• CSS/Sass
• Markdown

[hhochart]

Hey ! Little up for the JS syntax ! Is there any way to help you with this ? :)

[samrap]

I'd be happy to review any PRs if you wanna have a stab at it! I've been really busy at work so haven't had much time to work on this theme lately