Made a mass of accessibility improvements

- Changed default focus styles
- Updated dropdowns with keyboard navigation
- Updated modals with esc exiting
- Added accessibility attirbutes where needed
- Made many more elements focusable
- Updated hover effects of many items to also apply when focused within

Related to #1320 and #1198

resources/views/components/code-editor.blade.php

@@ -1,6 +1,6 @@
 <div id="code-editor">
     <div overlay ref="overlay" v-cloak @click="hide()">
-        <div class="popup-body" @click.stop>
+        <div class="popup-body" tabindex="-1" @click.stop>
 
             <div class="popup-header primary-background">
                 <div class="popup-title">{{ trans('components.code_editor') }}</div>

resources/views/components/entity-selector-popup.blade.php

@@ -1,6 +1,6 @@
 <div id="entity-selector-wrap">
     <div overlay entity-selector-popup>
-        <div class="popup-body small">
+        <div class="popup-body small" tabindex="-1">
             <div class="popup-header primary-background">
                 <div class="popup-title">{{ trans('entities.entity_select') }}</div>
                 <button type="button" class="popup-header-close">x</button>

resources/views/components/expand-toggle.blade.php

@@ -3,13 +3,13 @@ $target - CSS selector of items to expand
 $key - Unique key for checking existing stored state.
 --}}
 <?php $isOpen = setting()->getForCurrentUser('section_expansion#'. $key); ?>
-<a expand-toggle="{{ $target }}"
+<button type="button" expand-toggle="{{ $target }}"
    expand-toggle-update-endpoint="{{ url('/settings/users/'. $currentUser->id .'/update-expansion-preference/' . $key) }}"
    expand-toggle-is-open="{{ $isOpen ? 'yes' : 'no' }}"
    class="text-muted icon-list-item text-primary">
     <span>@icon('expand-text')</span>
     <span>{{ trans('common.toggle_details') }}</span>
-</a>
+</button>
 @if($isOpen)
     @push('head')
         <style>

resources/views/components/image-manager.blade.php

@@ -9,7 +9,7 @@
     ])
 
     <div overlay v-cloak @click="hide">
-        <div class="popup-body" @click.stop="">
+        <div class="popup-body" tabindex="-1" @click.stop>
 
             <div class="popup-header primary-background">
                 <div class="popup-title">{{ trans('components.image_select') }}</div>