Added examples, updated docs for image gallery api endpoints

[bookstack] / resources / views / common / custom-head.blade.php

@inject('headContent', 'BookStack\Theming\CustomHtmlHeadContentProvider')

@if(setting('app-custom-head') && !request()->routeIs('settings.category'))
<!-- Start: custom user content -->
{!! $headContent->forWeb() !!}
<!-- End: custom user content -->
@endif