Added an SVG icon for shuffle in dark theme

airsonic-main/src/main/resources/org/airsonic/player/theme/default_dark.properties

@@ -50,7 +50,7 @@ shareFacebookImage = icons/default_dark/share_facebook.png
 shareImage = icons/default_dark/share.png
 shareSmallImage = icons/default_dark/share_small.png
 shareTwitterImage = icons/default_dark/share_twitter.png
-shuffleImage = icons/default_dark/shuffle.png
+shuffleImage = icons/default_dark/shuffle.svg
 sidebarImage = icons/default_dark/sidebar.svg
 starredImage = icons/default_dark/starred.png
 statusImage = icons/default_dark/status.png

airsonic-main/src/main/webapp/icons/default_dark/shuffle.svg

@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#cdcdcd" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" class="feather feather-shuffle"><polyline points="16 3 21 3 21 8"></polyline><line x1="4" y1="20" x2="21" y2="3"></line><polyline points="21 16 21 21 16 21"></polyline><line x1="15" y1="15" x2="21" y2="21"></line><line x1="4" y1="4" x2="9" y2="9"></line></svg>