Minor changes to homepage

- Change subtitle to "Planta 8 - Tardor 2022"
- Center title and subtitle in the mobile view

Change-Id: Ifb81f0317898464ee69780388fb38aa0c70e6d79
diff --git a/css/login.css b/css/login.css
index a7c49b0..a875a88 100644
--- a/css/login.css
+++ b/css/login.css
@@ -9,6 +9,10 @@
 	.header-container {
 		flex-direction: column;
 	}
+
+	header {
+		text-align: center;
+	}
 }
 
 header h2 {
diff --git a/index.php b/index.php
index 1b87a7d..65baf23 100644
--- a/index.php
+++ b/index.php
@@ -35,7 +35,7 @@
 				<div class="header-container">
 					<header>
 						<h2>Carrot Cake</h2>
-						<h3>Facultat de Física - Tardor 2022</h3>
+						<h3>Planta 8 - Tardor 2022</h3>
 					</header>
 					<img src="/bin/images/vuit.png" class="logo">
 				</div>