Add support for custom themes - Vesper Theme

[ghost]

RunJS as a tool is amazing! However, there is a lack of touch in the customization of themes. Current themes are completely obsolete and tiring. An option could be added to add new themes or customize current ones.

Some good themes that could be added:

• Vesper
• Min Gruvbox
• Fleet theme

[lukehaas]

Thanks @senseeei. Custom themes are something I'd like to add support for in the future.

[Zumokame]

+1