Added volume slider

layout/sidebar/audioplayer.scarlet

@@ -1,6 +1,7 @@
 #audio-player
-	horizontal
+	vertical
 	default-transition
+	position relative
 	justify-content center
 	align-items center
 	margin 0.8rem 0
@@ -34,4 +35,47 @@
 		pointer-events none
 
 	.icon-play
-		transform translateX(3px)
+		transform translateX(3px)
+
+mixin volume-slider-thumb
+	appearance none
+	width 18px
+	height 18px
+	transform scale(0.5)
+	border-radius 50%
+	background text-color
+	cursor pointer
+	opacity 0.25
+	box-shadow shadow-medium
+	default-transition
+
+#audio-player-volume
+	appearance none
+	-webkit-appearance none
+	width 100%
+	height 6px
+	background rgba(0, 0, 0, 0.03)
+	outline none !important
+	border none !important
+	border-radius 0
+	padding 0
+	margin 0
+	margin-top 1rem
+
+	::-webkit-slider-thumb
+		volume-slider-thumb
+		-webkit-appearance none
+
+	::-moz-range-thumb
+		volume-slider-thumb
+
+	:active
+		transform none
+
+	:hover
+		background rgba(0, 0, 0, 0.06)
+
+		::-webkit-slider-thumb
+			background link-hover-color
+			opacity 1
+			transform scale(1)