PreviewTheme:
| "atom-dark.css"
| "atom-light.css"
| "atom-material.css"
| "github-dark.css"
| "github-light.css"
| "gothic.css"
| "medium.css"
| "monokai.css"
| "newsprint.css"
| "night.css"
| "none.css"
| "one-dark.css"
| "one-light.css"
| "solarized-dark.css"
| "solarized-light.css"
| "vue.css"