Add custom slider style

PlayWall/src/main/resources/style/components/slider.css

+.slider .track {
+	-fx-background-color: #5c5c5c;
+	-fx-background-radius: 3px;
+	-fx-background-insets: 1px;
+}
+
+.slider .thumb {
+	-fx-background-color: #CCCCCC;
+	-fx-padding: 0.333333em;
+	-fx-scale-x: 1.5;
+	-fx-scale-y: 1.5;
+}
\ No newline at end of file

PlayWall/src/main/scala/de/tobias/playpad/design/ModernGlobalDesignHandlerImpl.scala

@@ -31,6 +31,7 @@ class ModernGlobalDesignHandlerImpl extends ModernGlobalDesignHandler with Color
 		"style/components/scrollbar.css",
 		"style/components/textfield.css",
 		"style/components/radiobutton.css",
+		"style/components/slider.css",
 		"style/components/list.css",
 		"style/components/dialog.css"
 	)