window: Adjust to image size when opening

Give LpImage a native with that should feel nice.
When opening a new window with a new image the window size
is determined by LpImage's natural width.
The image size and EXIF data is loaded before the image such
that the window can be shown in the right dimension while
loading the actual image.

data/gtk/image_page.ui

@@ -53,11 +53,13 @@
           <object class="AdwStatusPage" id="error_page">
             <property name="icon-name">image-missing-symbolic</property>
             <property name="title" translatable="yes">Could not Load Image</property>
-            <property name="description" translatable="yes">This image could be corrupted or may use an unsupported file format.</property>
+            <property name="description" bind-source="LpImagePage" bind-property="error"/>
           </object>
         </child>
         <child>
           <object class="GtkScrolledWindow" id="scrolled_window">
+            <property name="propagate-natural-height">True</property>
+            <property name="propagate-natural-width">True</property>
             <property name="child">
               <object class="LpImage" id="image">
                 <child>

data/gtk/image_view.ui

@@ -5,7 +5,7 @@
     <property name="focusable">True</property>
     <property name="focus-on-click">True</property>
     <property name="child">
-      <object class="GtkOverlay">
+      <object class="GtkOverlay" id="bin_child">
         <property name="hexpand">True</property>
         <child>
           <object class="AdwCarousel" id="carousel">