Update EntityLoader docs

Change-Id: I5b87cc9a581267fab5a0c482f243f9e1d611423a
Reviewed-by: Tomi Korpipää <tomi.korpipaa@qt.io>
Reviewed-by: Sean Harmer <sean.harmer@kdab.com>

src/quick3d/quick3d/items/quick3dentityloader.cpp

@@ -93,7 +93,14 @@ private:
 /*!
     \qmltype EntityLoader
     \inqmlmodule Qt3D.Core
+    \inherits Entity
     \since 5.5
+    \brief Provides the facility to load entities from qml source
+
+    An EntityLoader provides the facitily to load predefined set of entities
+    from qml source file. EntityLoader itself is an entity and the loaded entity
+    tree is set as a child of the loader. The loaded entity tree root can be
+    accessed with EntityLoader::entity property.
 */
 Quick3DEntityLoader::Quick3DEntityLoader(QNode *parent)
     : QEntity(*new Quick3DEntityLoaderPrivate, parent)
@@ -107,7 +114,8 @@ Quick3DEntityLoader::~Quick3DEntityLoader()
 }
 
 /*!
-    \qmlproperty QtQml::QtObject Qt3DCore::EntityLoader::entity
+    \qmlproperty QtQml::QtObject EntityLoader::entity
+    Holds the loaded entity tree root.
     \readonly
 */
 QObject *Quick3DEntityLoader::entity() const
@@ -118,6 +126,7 @@ QObject *Quick3DEntityLoader::entity() const
 
 /*!
     \qmlproperty url Qt3DCore::EntityLoader::source
+    Holds the source url.
 */
 QUrl Quick3DEntityLoader::source() const
 {