Add GTK GUI frontend for whipper

data/com.github.whipper_team.Whipper.desktop

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+[Desktop Entry]
+Type=Application
+Version=1.0
+Name=Whipper
+GenericName=Audio CD Ripper
+Comment=Rip audio CDs with accuracy-focused whipper workflows
+Exec=whipper-gui
+Icon=com.github.whipper_team.Whipper
+Terminal=false
+Categories=AudioVideo;Audio;Music;GTK;
+Keywords=cd;ripper;accuraterip;musicbrainz;flac;
+StartupNotify=true

data/com.github.whipper_team.Whipper.metainfo.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<component type="desktop-application">
+  <id>com.github.whipper_team.Whipper</id>
+  <metadata_license>CC0-1.0</metadata_license>
+  <project_license>GPL-3.0-or-later</project_license>
+  <name>Whipper</name>
+  <developer_name>The Whipper Team</developer_name>
+  <summary>Accurate audio CD ripping with MusicBrainz metadata lookup</summary>
+  <description>
+    <p>
+      Whipper is an accuracy-focused audio CD ripper. The desktop frontend can
+      inspect the inserted disc, browse matching MusicBrainz releases, and run
+      secure ripping workflows backed by the existing whipper command-line
+      engine.
+    </p>
+  </description>
+  <launchable type="desktop-id">com.github.whipper_team.Whipper.desktop</launchable>
+  <url type="homepage">https://github.com/whipper-team/whipper</url>
+  <url type="bugtracker">https://github.com/whipper-team/whipper/issues</url>
+  <url type="help">https://github.com/whipper-team/whipper/blob/master/README.md</url>
+  <categories>
+    <category>AudioVideo</category>
+    <category>Audio</category>
+    <category>Music</category>
+  </categories>
+  <provides>
+    <binary>whipper</binary>
+    <binary>whipper-gui</binary>
+  </provides>
+</component>

data/com.github.whipper_team.Whipper.svg

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+<?xml version="1.0" encoding="UTF-8"?>
+<svg xmlns="http://www.w3.org/2000/svg" width="128" height="128" viewBox="0 0 128 128">
+  <rect width="128" height="128" rx="18" fill="#1f1f1f"/>
+  <rect x="10" y="10" width="108" height="108" rx="14" fill="#303030" stroke="#505050" stroke-width="4"/>
+  <circle cx="64" cy="64" r="38" fill="#404040" stroke="#8fb3ff" stroke-width="6"/>
+  <circle cx="64" cy="64" r="11" fill="#151515" stroke="#7f7f7f" stroke-width="4"/>
+  <path d="M84 30a40 40 0 0 1 14 10" fill="none" stroke="#d8e6ff" stroke-width="4" stroke-linecap="round"/>
+  <path d="M31 78h26" stroke="#8fb3ff" stroke-width="8" stroke-linecap="square"/>
+  <path d="M31 92h18" stroke="#d8e6ff" stroke-width="8" stroke-linecap="square"/>
+</svg>