Admin+Config: Add toggle that disables Cloudflare cache

It's now possible to disable the Cloudflare cache during development,
so the hacky workaround with the random number in the CSS/JS URLs is no
longer needed.

Development mode is automatically disabled by Cloudflare after 4 hours.

app/views/partials/admin.php

@@ -22,6 +22,9 @@
 		<br>
 		- <a href="<?= \App\Classes\Config::c('APP_URL'); ?>/admin/syntax-highlighting">Syntax Highlighting</a>
 
+		<hr>
+		<h5>Development mode&nbsp;&nbsp;<button id="development-mode" class="py-0 btn btn-dark">Enable</button></h5>
+
 		<hr>
 		- <a href="<?= \App\Classes\Config::c('APP_URL'); ?>/logout">Log out</a>
 	</div>