Correct file name of front image

Author: mcuntz

docs/html/_images/map_panel_dark_xr_ctk_screenshot.png

@@ -2,7 +2,7 @@
 Contents
 --------
 
-.. image:: ../images/map_panel_dark_xr_ctk_screenshot
+.. image:: ../images/map_panel_dark_xr_ctk_screenshot.png
    :width: 860 px
    :align: left
    :alt: Map panel of ncvue

docs/html/_sources/index.rst

@@ -381,7 +381,7 @@ <h1>Contents</h1>
 
   <section id="contents">
 <h1>Contents<a class="headerlink" href="#contents" title="Link to this heading">#</a></h1>
-<a class="reference internal image-reference" href="../images/map_panel_dark_xr_ctk_screenshot"><img alt="Map panel of ncvue" class="align-left" src="../images/map_panel_dark_xr_ctk_screenshot" style="width: 860px;" />
+<a class="reference internal image-reference" href="_images/map_panel_dark_xr_ctk_screenshot.png"><img alt="Map panel of ncvue" class="align-left" src="_images/map_panel_dark_xr_ctk_screenshot.png" style="width: 860px;" />
 </a>
 <div class="toctree-wrapper compound">
 <ul>

docs/html/_static/authors.rst

@@ -2,7 +2,7 @@
 Contents
 --------
 
-.. image:: ../images/map_panel_dark_xr_ctk_screenshot
+.. image:: ../images/map_panel_dark_xr_ctk_screenshot.png
    :width: 860 px
    :align: left
    :alt: Map panel of ncvue