add AppStream metadata as a desktop application component

Link: https://www.freedesktop.org/software/appstream/docs/chap-Metadata.html

Signed-off-by: Markus Göllnitz <camelcasenick@bewares.it>

Author: camelCaseNick

build.gradle

@@ -219,6 +219,7 @@ distZip {
     from 'xdg'
     include '**/*.desktop'
     include '**/*.png'
+    include '**/*.xml'
     include 'prepare*.sh'
   }
   // legal stuff, examples, and documentation

xdg/metainfo/io.github.mgoellnitz.JFileSync3.metainfo.xml

@@ -0,0 +1,69 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<component type="desktop-application">
+  <id>io.github.mgoellnitz.JFileSync3</id>
+  <project_license>GPL-3.0-or-later</project_license>
+  <metadata_license>CC0-1.0</metadata_license>
+  <name>JFileSync3</name>
+  <summary>Java based encrypting File Syncing Tool</summary>
+  <launchable type="desktop-id">io.github.mgoellnitz.JFileSync3.desktop</launchable>
+  <content_rating type="oars-1.1"/>
+  <developer_name>Martin Göllnitz</developer_name>
+  <developer id="io.github.mgoellnitz">
+    <name>Martin Göllnitz</name>
+  </developer>
+
+  <categories>
+    <category>Java</category>
+    <category>Archiving</category>
+    <category>Utility</category>
+  </categories>
+
+  <url type="homepage">https://mgoellnitz.github.io/JFileSync3/</url>
+  <url type="bugtracker">https://github.com/mgoellnitz/JFileSync3/issues</url>
+  <url type="donation">https://ko-fi.com/backendzeit</url>
+  <url type="vcs-browser">https://github.com/mgoellnitz/JFileSync3</url>
+
+  <description>
+    <p>
+      File syncing with optional compression and encryption for local and 
+      WebDAV folders. For local folders, encryption can optionally be 
+      accomplished with EncFS and thus be compatible with encfs4win, EDS Lite, 
+      Encdroid and so on.
+    </p>
+  </description>
+
+  <releases>
+    <release version="3.0.17" date="2022-09-25"/>
+    <release version="3.0.16" date="2021-11-24"/>
+    <release version="3.0.15" date="2018-03-27"/>
+    <release version="3.0.14" date="2016-12-29"/>
+    <release version="3.0.13" date="2015-10-11"/>
+    <release version="3.0.12" date="2015-10-06"/>
+    <release version="3.0.11" date="2015-09-27"/>
+    <release version="3.0.10" date="2015-08-17"/>
+    <release version="3.0.9" date="2015-07-12"/>
+  </releases>
+
+  <screenshots>
+    <screenshot type="default">
+      <image>https://raw.githubusercontent.com/mgoellnitz/JFileSync3/master/screenshots/screenshot-sync-local.png</image>
+    </screenshot>
+  </screenshots>
+
+  <provides>
+    <binary>JFileSync3</binary>
+  </provides>
+
+  <supports>
+    <control>touch</control>
+  </supports>
+  <recommends>
+    <control>pointing</control>
+    <control>keyboard</control>
+    <display_length compare="ge" side="shortest">600</display_length>
+    <display_length compare="ge" side="longest">720</display_length>
+  </recommends>
+  <requires>
+    <display_length compare="ge" side="longest">500</display_length>
+  </requires>
+</component>