Move largest Greetings Window assets to cloudflare CDN (#9649)

Modified the Greetings Window to download things from the Cloudflare CDN, instead of relying on the assets cache.

Reasons:

    CDN is faster and better for world wide (Aussie) users.
    IE caches these files in the background. Since they're static, this will mean faster loading times even if BYOND deletes the BYOND cache (since IE cache and BYOND cache are separate).
    If other UI frameworks do the same, we cut down on the initial transfer and load times A LOT by sharing the same cached and CDN-d resources.

code/modules/client/asset_cache.dm

@@ -169,9 +169,6 @@ var/list/asset_datums = list()
 		"search.js" = 'html/search.js',
 		"panels.css" = 'html/panels.css',
 		"loading.gif" = 'html/images/loading.gif',
-		"bootstrap.min.css" = 'html/bootstrap/css/bootstrap.min.css',
-		"bootstrap.min.js" = 'html/bootstrap/js/bootstrap.min.js',
-		"jquery-2.0.0.min.js" = 'html/jquery/jquery-2.0.0.min.js',
 		"ie-truth.min.js" = 'html/iestats/ie-truth.min.js',
 		"conninfo.min.js" = 'html/iestats/conninfo.min.js',
 		"copyright_infrigement.png" = 'html/copyright_infrigement.png'

html/changelogs/skull132_cdning-welcome-screen.yml

@@ -0,0 +1,5 @@
+author: Skull132
+delete-after: True
+
+changes:
+  - backend: "The Welcome Window now uses resources from the Cloudflare CDN. This should make resource downloading faster."

html/templates/welcome_screen.html

@@ -5,7 +5,10 @@
 		<meta http-equiv="X-UA-Compatible" content="IE=edge">
 		<meta name="viewport" content="width=device-width, initial-scale=1">
 		<!-- Bootstrap -->
-		<link href="bootstrap.min.css" rel="stylesheet" media="screen">
+		<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.5.1/jquery.min.js" crossorigin="anonymous"></script>
+		<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.4.1/css/bootstrap.min.css" crossorigin="anonymous" />
+		<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.4.1/css/bootstrap-theme.min.css" crossorigin="anonymous" />
+		<script src="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.4.1/js/bootstrap.min.js" crossorigin="anonymous"></script>
 		<style media="screen">
 			.nav-tabs>li.updated>a, .nav-tabs>li.updated>a:hover, .nav-tabs>li.updated>a:focus {
 				background-color: #fcf8e3;
@@ -60,8 +63,6 @@
 		</div>
 	</body>
 
-	<script src="jquery-2.0.0.min.js"></script>
-	<script src="bootstrap.min.js"></script>
 	<script src="ie-truth.min.js"></script>
 	<script src="conninfo.min.js"></script>
 	<script type="text/javascript">
@@ -137,7 +138,7 @@
 		}
 
 		// DOM ready function.
-		$(document).ready(function () {
+		$(function () {
 			// Handle tabs (mostly bootstrap).
 			$('#myTab a').click(function (e) {
 				e.preventDefault();
@@ -171,7 +172,7 @@
 
 
 			// Operations before closing.
-			$(window).unload(function() {
+			$(window).on('unload', function() {
 				try {
 					window.location = '?JSlink=updateHashes;' + jQuery.param(hashesToUpdate);
 				} catch (e) { }