A11y improvements and style tweaks

- Use button element instead of anchors, fixes keyboard navigation and
other issues
- Disable search input until it's open, prevents being able to write
inside it while it's closed
- Use :root instead of html in CSS
- Add minimal size for separator between home button and other links

sass/_general.scss

@@ -4,7 +4,7 @@
 	box-sizing: border-box;
 }
 
-html {
+:root {
 	text-wrap: pretty;
 	scroll-behavior: smooth;
 	// scrollbar-color: var(--primary-color) transparent;
@@ -18,15 +18,10 @@ html {
 	// }
 }
 
-html,
-body {
-	margin: 0;
-	padding: 0;
-}
-
 body {
 	display: grid; // Put footer at the bottom for short pages, such as the 404
 	grid-template-rows: auto minmax(auto, 1fr) auto; // Header, stuff, footer
+	margin: 0;
 	background: var(--bg-color), var(--primary-color);
 	min-height: 100vh;
 	color: var(--fg-color);