fix(MdSteppers): recalculate styles on window resize (vuematerial#1394)

* fix(MdSteppers): overflow on resize

* refactor(MdSteppers): add beforeDestroy hook to remove resize listener

Author: Samuell1

src/components/MdSteppers/MdSteppers.vue

@@ -186,6 +186,8 @@
         if ('ResizeObserver' in window) {
           this.resizeObserver = new window.ResizeObserver(this.calculateStepperPos)
           this.resizeObserver.observe(this.$el)
+        } else {
+           window.addEventListener('resize', this.calculateStepperPos)
         }
 
         if (steppersContent) {
@@ -244,7 +246,12 @@
         this.setupObservers()
         this.setupWatchers()
       }, 100)
-    }
+    },
+    beforeDestroy () {
+      if (!('ResizeObserver' in window)) {
+        window.removeEventListener('resize', this.calculateStepperPos)
+      }
+    },
   })
 </script>