Update banner title and link for 2.0 site

Author: ksen0

src/content/banner/en.mdx

@@ -1,8 +1,8 @@
 ---
 # Give each new message a unique title so we know which one a user closed
-title: "old-site"
-link: "https://archive.p5js.org"
+title: "beta-site"
+link: "https://beta.p5js.org"
 hidden: false
 ---
 
-Looking for the old p5.js site? Find it here!
+Looking for the p5.js 2.0 reference? Find it here!