feat: add codeium meta in head

Signed-off-by: Yukai Huang <yukaihuangtw@gmail.com>

Author: Yukaii

public/views/codimd/head.ejs

@@ -4,6 +4,7 @@
 <meta name="apple-mobile-web-app-capable" content="yes">
 <meta name="apple-mobile-web-app-status-bar-style" content="black">
 <meta name="mobile-web-app-capable" content="yes">
+<meta name="codeium:type" content="codemirror5">
 <title><%= title %></title>
 <link rel="icon" type="image/png" href="<%- serverURL %>/favicon.png">
 <link rel="apple-touch-icon" href="<%- serverURL %>/apple-touch-icon.png">