First implementation of dark mode

frontend/src/customTheme.js

@@ -0,0 +1,27 @@
+import { Themes } from '@geist-ui/core'
+
+const customDarkTheme = Themes.createFromLight({
+  type: 'custom-dark',
+  palette: {
+    background: '#1e1e1e',
+    foreground: '#d4d4d4',
+    selection: '#2c313a',
+    secondary: '#858585',
+    code: '#d4d4d4',
+    border: '#333333',
+    success: '#4EC9B0',
+    warning: '#9CDCFE',
+    error: '#F44747',
+  },
+  expressiveness: {
+    dropdownBoxShadow: '0 0 0 1px #333333',
+    shadowSmall: '0 0 0 1px #333333',
+    shadowMedium: '0 0 0 1px #333333',
+    shadowLarge: '0 0 0 1px #333333',
+  },
+})
+
+export const customTheme = {
+  light: Themes.light,
+  dark: customDarkTheme,
+}