[fix] added captions

Author: n3kosempai

io.github.N3kosempai.klia-store.metainfo.xml

@@ -17,15 +17,19 @@
   <url type="vcs-browser">https://github.com/N3koSempai/klia-store</url>
   <screenshots>
     <screenshot type="default">
+      <caption>Main application window showing start page</caption>
       <image>https://raw.githubusercontent.com/N3koSempai/klia-store/master/screenshots/screenshot1.png</image>
     </screenshot>
     <screenshot>
+      <caption>Application details view with description and installation options</caption>
       <image>https://raw.githubusercontent.com/N3koSempai/klia-store/master/screenshots/screenshot2.png</image>
     </screenshot>
     <screenshot>
+      <caption>Installed applications management interface</caption>
       <image>https://raw.githubusercontent.com/N3koSempai/klia-store/master/screenshots/screenshot3.png</image>
     </screenshot>
     <screenshot>
+      <caption>Modal for updating a specific application</caption>
       <image>https://raw.githubusercontent.com/N3koSempai/klia-store/master/screenshots/screenshot4.png</image>
     </screenshot>
   </screenshots>