Refactor welcome message in index.vue (#8)

- Change "Bem-vindo" to "Olá"
- Update welcome message to include user's first name if available

Co-authored-by: Gabriel Lyra <gmlyra@live.com>

apps/app/pages/index.vue

@@ -2,7 +2,7 @@
 const userStore = useUserStore();
 
 const title = computed(() => {
-  return `Bem-vindo${
+  return `Olá${
     userStore.user?.firstName ? `, ${userStore.user.firstName}` : ""
   }, o que vamos aprender hoje?`;
 });