initial Auth implementation (#44)

* initial implementation

* update api url

src/Auth.tsx

@@ -0,0 +1,31 @@
+import useSWR from 'swr'
+import fetcher from './lib/fetcher'
+import withBaseUrl from './lib/withBaseURL'
+import App from './App'
+
+export const Auth = () => {
+  const { data: user, error } = useSWR(withBaseUrl('/user'), fetcher) as any
+  const isLocalHost =
+    typeof window !== 'undefined' && window.location.hostname === 'localhost'
+
+  if (!user && !isLocalHost) {
+    return (
+      <>
+        <div className=" bg-gray-800 p-1 px-4 rounded-r-lg pointer-events-auto flex items-center">
+          <a
+            className="font-bold mr-2 text-purple-400"
+            rel="noopener noreferrer"
+            target={'_self'}
+            href={`https://dev.kittycad.io/signin?callbackUrl=${encodeURIComponent(
+              typeof window !== 'undefined' && window.location.href
+            )}`}
+          >
+            Sign in
+          </a>
+        </div>
+      </>
+    )
+  }
+
+  return <App />
+}