Add Linux metadata files (mbrlabs#203)

* Add Linux meta files

* Linux Meta: Update translations

* Linux Meta: Change mime type to x-lorien-canvas

public/linux/com.github.mbrlabs.Lorien.desktop

@@ -0,0 +1,13 @@
+[Desktop Entry]
+Type=Application
+Name=Lorien
+GenericName=Note Taking
+Comment=Infinite canvas drawing/whiteboarding app
+Comment[de]=Freie Zeichen- und Whiteboard-App
+Icon=com.github.mbrlabs.Lorien
+Exec=Lorien %U
+Terminal=false
+MimeType=application/lorien
+Categories=Graphics;
+Keywords=Drawing;Handwriting;Whiteboard
+StartupWMClass=Lorien

public/linux/com.github.mbrlabs.Lorien.metainfo.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<component type="desktop-application">
+  <id>com.github.mbrlabs.Lorien</id>
+
+  <name>Lorien</name>
+  <summary>Infinite canvas drawing/whiteboarding app</summary>
+  <summary xml:lang="de_DE">Freie Zeichen- und Whiteboard-App</summary>
+
+  <url type="homepage">https://github.com/mbrlabs/Lorien</url>
+  <url type="bugtracker">https://github.com/mbrlabs/Lorien/issues</url>
+  <url type="help">https://github.com/mbrlabs/Lorien/blob/main/docs/manuals</url>
+  <url type="donation">https://ko-fi.com/mbrlabs</url>
+  <url type="translate">https://github.com/mbrlabs/Lorien/blob/main/docs/i18n.md</url>
+
+  <metadata_license>CC0-1.0</metadata_license>
+  <project_license>MIT</project_license>
+  <content_rating type="oars-1.1"/>
+
+  <launchable type="desktop-id">com.github.mbrlabs.Lorien.desktop</launchable>
+
+  <description>
+    <p>Lorien is an infinite canvas drawing/note-taking app that is focused on performance, small savefiles and simplicity.</p>
+    <p>It's not based on bitmap images like Krita, Gimp or Photoshop; it rather saves brush strokes as a collection of points and renders them at runtime (kind of like SVG).</p>
+    <p>It's primarily designed to be used as a digital notebook and as brainstorming tool.</p>
+    <p>While it can totally be used to make small sketches and diagrams, it is not meant to replace traditional art programs that operate on bitmap images.</p>
+    <p>It is entirely written in the Godot Game Engine.</p>
+  </description>
+
+  <screenshots>
+    <screenshot type="default">
+      <image>https://raw.githubusercontent.com/mbrlabs/Lorien/main/images/lorien_demo.png</image>
+    </screenshot>
+  </screenshots>
+
+  <releases>
+    <release version="0.5.0" date="2022-06-12"/>
+  </releases>
+</component>

public/linux/x-lorien-canvas.mimetype.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<mime-info xmlns="http://www.freedesktop.org/standards/shared-mime-info">
+   <mime-type type="application/x-lorien-canvas">
+     <comment>Lorien Canvas file</comment>
+     <comment xml:lang="de">Lorien Zeichnung</comment>
+     <glob pattern="*.lorien"/>
+   </mime-type>
+</mime-info>