initial work on a bootstrap 5 template

current status:
- renders without PHP errors & passes unit tests
- displays pastes
- responsive navbar
- right-to-left support
- auto dark mode with toggle

to be done:
- add "Dark Mode" to translation strings
- get expiration and format selections to work
- fix modals (password, QR-code, etc.)
- replace glyphicons with Bootstrap Icons (no longer included)
- test all the different settings and combinations
- check tab alignment in HTML source

lib/View.php

@@ -50,7 +50,7 @@ class View
      */
     public function draw($template)
     {
-        $file = substr($template, 0, 9) === 'bootstrap' ? 'bootstrap' : $template;
+        $file = substr($template, 0, 10) === 'bootstrap-' ? 'bootstrap' : $template;
         $path = PATH . 'tpl' . DIRECTORY_SEPARATOR . $file . '.php';
         if (!file_exists($path)) {
             throw new Exception('Template ' . $template . ' not found!', 80);