web: fix typos and add link to discord

web/app/header.tsx

-
 const navigation = [
-  { name: 'Github', href: 'https://github.com/jmorganca/ollama' },
+  { name: 'Discord', href: 'https://discord.gg/MrfB5FbNWN' },
+  { name: 'GitHub', href: 'https://github.com/jmorganca/ollama' },
   { name: 'Download', href: '/download' },
 ]
 
 export default function Header() {
   return (
-    <header className="absolute inset-x-0 top-0 z-50">
-      <nav className="mx-auto flex items-center justify-between px-10 py-4">
-        <a className="flex-1 font-bold" href="/">
+    <header className='absolute inset-x-0 top-0 z-50'>
+      <nav className='mx-auto flex items-center justify-between px-10 py-4'>
+        <a className='flex-1 font-bold' href='/'>
           Ollama
         </a>
-        <div className="flex space-x-8">
-          {navigation.map((item) => (
-            <a key={item.name} href={item.href} className="text-sm leading-6 text-gray-900">
+        <div className='flex space-x-8'>
+          {navigation.map(item => (
+            <a key={item.name} href={item.href} className='text-sm leading-6 text-gray-900'>
               {item.name}
             </a>
           ))}
         </div>
       </nav>
-    </header >
+    </header>
   )
-}
\ No newline at end of file
+}