feat: specify theme colours

src/styles.css

···
     --font-sans: 'Hanken Grotesk Variable', sans-serif;
     --font-serif: 'Amiri', serif;
     --font-mono: 'Maple Mono', monospace;
+
+    --color-strand-crust: oklch(0.1286 0 0);
+    --color-strand-mantle: oklch(0.1776 0 0);
+    --color-strand-base: oklch(0.209 0 0);
+
+    --color-strand-text: oklch(0.9911 0 0);
+    --color-strand-subtext: oklch(0.9521 0 0);
+    --color-strand-overlay: oklch(0.9143 0 0)
 }
 
 body {