Made another mass of accessibility improvements

- Set proper semantic tags for main parts of content.
- Removed focus-trap from tag manager/autosuggest.
- Set better accessibility labelling on tag manager.
- Updated collapsible sections to be keyboard navigatable.
- Improved input focus styling to better fit theme.
- Updated custom styled file picker to be accessible via keyboard.

Related to #1320

resources/lang/en/common.php

@@ -59,6 +59,7 @@ return [
     'grid_view' => 'Grid View',
     'list_view' => 'List View',
     'default' => 'Default',
+    'breadcrumb' => 'Breadcrumb',
 
     // Header
     'profile_menu' => 'Profile Menu',