Add deprecation notice

package.json

@@ -1,6 +1,6 @@
 {
     "name": "@fwdekker/template",
-    "version": "2.2.3",
+    "version": "2.2.4",
     "description": "The base template for pages on fwdekker.com.",
     "author": "Felix W. Dekker",
     "license": "MIT",

src/main/js/main.js

@@ -191,6 +191,8 @@ const footerLink = function(prefix, text, url, suffix) {
 
 /**
  * Unhides the main element on the page and applies default display styling.
+ *
+ * @deprecated Will be removed in the near future. Just use `$("main").classList.remove("hidden")` yourself.
  */
 const showPage = function() {
     const main = $("main");