help: Write intial help documentation

Part-of: <https://gitlab.gnome.org/GNOME/Incubator/loupe/-/merge_requests/248>

help/C/image-properties.page

@@ -0,0 +1,37 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  DO NOT EDIT THIS FILE!
+
+  This file is autogenerated with ducktype.
+  Edit duck/image-properties.page.duck instead and run make in this directory.
+-->
+<page xmlns="http://projectmallard.org/1.0/" type="topic" id="image-properties">
+ <info>
+  <link type="guide" xref="index#additional-features"/>
+  <desc>View detailed properties of the selected image.</desc>
+ </info>
+ <title>Image Properties</title>
+ <p>Loupe allows users to view an image's properties. All images will have the following
+ basic properties:</p>
+ <list>
+  <item>
+   <p>Image size</p>
+  </item>
+  <item>
+   <p>Image format</p>
+  </item>
+  <item>
+   <p>File size</p>
+  </item>
+  <item>
+   <p>File creation date</p>
+  </item>
+  <item>
+   <p>File modification date</p>
+  </item>
+ </list>
+ <p>If the file has <link href="https://en.wikipedia.org/wiki/Exif">Exif</link> metadata, it
+ will be shown below the basic properties.</p>
+ <p>To view the selected image's properties, press the <gui>Image Properties</gui>
+ (<media type="image" src="figures/help-about-symbolic.svg">help-about-symbolic</media>) button.</p>
+</page>