Add icon to device class duration (#13961)

* Add icon to device class duration

* Change to mdiProgressClock

src/common/const.ts

@@ -43,6 +43,7 @@ import {
   mdiMoleculeCo,
   mdiMoleculeCo2,
   mdiPalette,
+  mdiProgressClock,
   mdiRayVertex,
   mdiRemote,
   mdiRobot,
@@ -125,6 +126,7 @@ export const FIXED_DEVICE_CLASS_ICONS = {
   current: mdiCurrentAc,
   date: mdiCalendar,
   distance: mdiArrowLeftRight,
+  duration: mdiProgressClock,
   energy: mdiLightningBolt,
   frequency: mdiSineWave,
   gas: mdiMeterGas,