Improve handling the case when the latest release doesn't provide ass…

…ets yet

Show assets from the next most recent release instead. This is still not
perfect because if assets of a platform have already been uploaded
partially the page would still only show a partial list.

css/specifics.css

@@ -147,6 +147,10 @@
     border: 1px solid #ddd;
     background-color: #e5f3ff;
 }
+.download-remark {
+    color: #555;
+    font-style: italic;
+}
 
 /* elements of the documentation section */
 #doc-section p {

index.html

@@ -146,13 +146,13 @@ <h3>Official downloads</h3>
             </div>
             <div class="downloads-platform">
               <input type="checkbox" id="downloads-checkbox-pc-linux-gnu"/><label for="downloads-checkbox-pc-linux-gnu">GNU/Linux</label>
-              <ul id="downloads-platform-pc-linux-gnu"></ul>
+              <ul id="downloads-platform-pc-linux-gnu" class="download-list-important"></ul>
               <p>Requires <code>glibc>=2.26</code>, OpenGL and libX11. The distributions openSUSE Leap 15, Fedora 27, Debian 10 and Ubuntu 18.04 are recent enough (be sure the package <code>libopengl0</code> is installed on Debian/Ubuntu).</p>
               <p>These downloads cannot include the Plasmoid/Applet (for the Plasma desktop) and the Dolphin integration for technical reasons. The KDE integrations therefore need to be installed via distribution-specific packages.</p>
             </div>
             <div class="downloads-platform">
               <input type="checkbox" id="downloads-checkbox-windows10"/><label for="downloads-checkbox-windows10">Windows 10 and 11</label>
-              <ul id="downloads-platform-windows10"></ul>
+              <ul id="downloads-platform-windows10" class="download-list-important"></ul>
               <p>
                 These downloads require Windows 10 version 1809 or newer.
               </p>
@@ -168,7 +168,7 @@ <h3>Official downloads</h3>
             </div>
             <div class="downloads-platform">
               <input type="checkbox" id="downloads-checkbox-windows"/><label for="downloads-checkbox-windows">Windows 7 and newer</label>
-              <ul id="downloads-platform-windows"></ul>
+              <ul id="downloads-platform-windows" class="download-list-important"></ul>
               <p>
                 On Windows 7 the bundled Go/Syncthing does not work. Use a version of Go/Syncthing that is older than 1.21/1.27.0 instead.
               </p>