added basic styling of slides

src/ui/src/assets/css/_slide.scss

@@ -1,5 +1,20 @@
 .slide {
+	font-family: "Iosevka", sans-serif;
+	font-size: 2rem;
+	display: flex;
+	align-items: center;
+	justify-content: center;
 	user-select: none;
+	aspect-ratio: 1.333;
 	background: color(background);
 	color: color(foreground);
+
+	h1 {
+		font-size: 4rem;
+	}
+
+	code {
+		font-size: 1.2rem;
+		width: 90%;
+	}
 }