templates: update script tags for ES modules and reader link

- Change script tags from 'defer' to 'type=module' for ES module support
- Add reader.js script to reader.templ for the reader bundle
- Update book_detail.templ 'Read Now' button to link to /readers/{id}
- Remove trailing blank line from register.templ

templates/reader.templ

@@ -12,7 +12,7 @@ templ Reader(user User, metadata ReaderMetadata, progress ReadingProgress, bookm
 			<link rel="manifest" href="/static/manifest.json"/>
 			<link href="/static/reader-fonts.css" rel="stylesheet"/>
 			<script src="/static/htmx.min.js"></script>
-			<script src="/static/main.js" defer></script>
+			<script type="module" src="/static/reader.js"></script>
 			<link href="/static/style.css" rel="stylesheet"/>
 		</head>
 		<body