Dark mode styles for Ghost Solo theme

dark.css

@media (prefers-color-scheme: dark) {
     :root {
         --background-color: #1a1a1a;
         --color-primary-text: #e3e3e3;
         --color-secondary-text-dark: rgba(255, 255, 255, 0.65);
         --color-secondary-text-light: rgba(0, 0, 0, 0.8);
         --color-secondary-text: var(--color-secondary-text-dark);
         --color-darker-gray: #e1e1e1;
         --color-lighter-gray: #000;
         --color-border: rgba(255, 255, 255, 0.08);
    }
     .has-background-about .gh-subscribe-input {
         color: var(--color-secondary-text-dark);
         background-color: #3e3e3e;
         border: 0;
    }
}