style(ui): use Merriweather serif for chat text and Encode Sans for the rest of the UI

tailwind.config.js

@@ -14,6 +14,10 @@ export default {
       },
     },
     extend: {
+      fontFamily: {
+        sans: ['"Encode Sans"', '-apple-system', 'BlinkMacSystemFont', '"Segoe UI"', 'Roboto', '"Helvetica Neue"', 'Arial', 'sans-serif'],
+        serif: ['Merriweather', 'Georgia', 'Cambria', '"Times New Roman"', 'serif'],
+      },
       colors: {
         border: "hsl(var(--border))",
         input: "hsl(var(--input))",