accessibility: add shortcuts to mute camera/mic during a call

Change-Id: Ib125fcac0620326d5864e577d9252e9ea9b3c3d9
GitLab: #788

src/app/mainview/components/KeyboardShortcutTable.qml

@@ -151,6 +151,14 @@ Window {
             shortcut: "Ctrl + Shift + D"
             description: qsTr("Decline the call request")
         }
+        ListElement {
+            shortcut: "M"
+            description: qsTr("Mute the microphone (during a call)")
+        }
+        ListElement {
+            shortcut: "V"
+            description: qsTr("Mute the camera (during a call)")
+        }
     }
 
     Rectangle {

src/app/mainview/components/MainOverlay.qml

@@ -72,6 +72,29 @@ Item {
         }
     }
 
+
+    Shortcut {
+        sequence: "M"
+        enabled: root.visible
+        context: Qt.ApplicationShortcut
+        onActivated: {
+            CallAdapter.muteAudioToggle()
+            root.opacity = 1
+            fadeOutTimer.restart()
+        }
+    }
+
+    Shortcut {
+        sequence: "V"
+        enabled: root.visible
+        context: Qt.ApplicationShortcut
+        onActivated: {
+            CallAdapter.muteCameraToggle()
+            root.opacity = 1
+            fadeOutTimer.restart()
+        }
+    }
+
     // control overlay fade out.
     Timer {
         id: fadeOutTimer