add meta files for linux

build/linux/PpdEditor.desktop

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+[Desktop Entry]
+Type=Application
+Name=PpdEditor
+GenericName=Paperdoll Editor
+Comment=Editor for 2D paperdoll file
+Icon=io.github.fralonra.PpdEditor
+Exec=ppd-editor
+Terminal=false
+Categories=Graphics;2DGraphics;

build/linux/PpdEditor.metainfo.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<component type="desktop-application">
+    <id>io.github.fralonra.PpdEditor</id>
+    <name>PpdEditor</name>
+    <developer_name>fralonra</developer_name>
+    <summary>Editor for 2D paperdoll file</summary>
+    <metadata_license>CC0-1.0</metadata_license>
+    <project_license>MIT</project_license>
+    <description>
+        <p>
+            Editor and viewer for paperdoll, a 2D pixel-based stationary paper doll model.
+        </p>
+    </description>
+    <categories>
+        <category>Graphics</category>
+        <category>2DGraphics</category>
+    </categories>
+    <keywords>
+        <keyword>graphics</keyword>
+        <keyword>gamedev</keyword>
+        <keyword>paperdoll</keyword>
+    </keywords>
+    <url type="homepage">https://github.com/fralonra/ppd-editor/</url>
+    <url type="bugtracker">https://github.com/fralonra/ppd-editor/issues</url>
+    <launchable type="desktop-id">io.github.fralonra.PpdEditor.desktop</launchable>
+    <releases>
+        <release version="0.1.0" date="2023-08-10"/>
+    </releases>
+    <screenshots>
+        <screenshot type="default">
+            <image>https://raw.githubusercontent.com/fralonra/ppd-editor/master/resources/docs/ppd-editor.png</image>
+        </screenshot>
+        <screenshot>
+            <image>https://raw.githubusercontent.com/fralonra/ppd-editor/master/resources/docs/ppd-viewer.png</image>
+        </screenshot>
+    </screenshots>
+    <content_rating type="oars-1.1" />
+</component>

build/linux/PpdViewer.desktop

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+[Desktop Entry]
+Type=Application
+Name=PpdViewer
+GenericName=Paperdoll Viewer
+Comment=Viewer for 2D paperdoll file
+Icon=io.github.fralonra.PpdViewer
+Exec=ppd-viewer
+Terminal=false
+Categories=Graphics;2DGraphics;