frontend: Add headphones icon in Light Theme

frontend/data/themes/Light/headphones-off.svg

@@ -0,0 +1 @@
+<svg version="1.2" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 160 160" width="160" height="160"><style>.a{fill:#202020;opacity:0.4;}.b{fill:#202020}</style><path class="a" d="m150 65.6c0-25-13-43.6-35-56.6-11-6-23-9-35-9-12 0-24 3-35 9-22 13-35 36-35 61v60c0 0 0 20 20 20h10c6 0 10-4 10-10v-40c0-6-5-10-10-10 0 0-10 0-10-10v-10c0-18 10-34 25-43 15-9 35-9 50 0 15 9 25.5 22.5 25.5 40.8l19.5-0.2z"/><path class="b" d="m90 78q-4.8 0-8.4 3.6c-4.8 4.8-4.8 12 0 16.8l15.6 15.6-15.6 15.6c-4.8 4.8-4.8 12 0 16.8 4.8 4.8 12 4.8 16.8 0l15.6-15.6 15.6 15.6c4.8 4.8 12 4.8 16.8 0 4.8-4.8 4.8-12 0-16.8l-15.6-15.6 15.6-15.6c4.8-4.8 4.8-12 0-16.8q-3.6-3.6-8.4-3.6-4.8 0-8.4 3.6l-15.6 15.6-15.6-15.6q-3.6-3.6-8.4-3.6z"/></svg>

frontend/data/themes/Light/headphones.svg

@@ -0,0 +1 @@
+<svg version="1.2" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 16 16" width="16" height="16"><style>.a{fill:#202020}</style><path class="a" d="m8 0c-1.2 0-2.4 0.3-3.5 0.9-2.2 1.3-3.5 3.6-3.5 6.1v6c0 0 0 2 2 2h1c0.6 0 1-0.4 1-1v-4c0-0.6-0.5-1-1-1 0 0-1 0-1-1v-1c0-1.8 1-3.4 2.5-4.3 1.5-0.9 3.5-0.9 5 0 1.5 0.9 2.5 2.5 2.5 4.3v1c0 1-1 1-1 1-0.5 0-1 0.4-1 1v4c0 0.6 0.4 1 1 1h1c2 0 2-2 2-2v-6c0-2.5-1.3-4.8-3.5-6.1-1.1-0.6-2.3-0.9-3.5-0.9z"/></svg>

frontend/data/themes/Yami_Light.ovt

@@ -44,6 +44,26 @@
     --scrollbar_border: var(--grey7);
 }
 
+/* Mute Button */
+
+.btn-mute {
+    qproperty-icon: url(theme:Light/settings/audio.svg);
+}
+
+.btn-mute.checked {
+    qproperty-icon: url(theme:Light/mute.svg);
+}
+
+/* Monitor Button */
+
+.btn-monitor {
+    qproperty-icon: url(theme:Light/headphones-off.svg);
+}
+
+.btn-monitor.checked {
+    qproperty-icon: url(theme:Light/headphones.svg);
+}
+
 VolumeMeter {
     qproperty-backgroundNominalColor: var(--green4);
     qproperty-backgroundWarningColor: var(--yellow4);