Material Darker theme

Inspired by

• https://github.com/atom-material/atom-material-syntax-dark

Thanks to these guys for doing a working material theme for VSCode

• https://marketplace.visualstudio.com/items?itemName=artemmalko.theme-material-neutral-no-underline
• https://marketplace.visualstudio.com/items?itemName=bernardodsanderson.theme-material-neutral

The theme is based on these, but with a darker background color which blends better with the UI.