allow burndown chart to resize during animations

app/assets/javascripts/burndown_chart/burndown_chart.js

@@ -120,4 +120,18 @@ export default class BurndownChart {
       this.idealLinePath.datum(this.idealData).attr('d', this.line);
     }
   }
+
+  animate(seconds = 5) {
+    this.ticksLeft = this.ticksLeft || 0;
+    if (this.ticksLeft <= 0) {
+      const interval = setInterval(() => {
+        this.ticksLeft -= 1;
+        if (this.ticksLeft <= 0) {
+          clearInterval(interval);
+        }
+        this.resize();
+      }, 20);
+    }
+    this.ticksLeft = seconds * 50;
+  }
 }

app/assets/javascripts/burndown_chart/index.js

@@ -18,5 +18,6 @@ $(() => {
   });
 
   chart.setData(testData);
-  window.addEventListener('resize', () => chart.resize());
+  window.addEventListener('resize', () => chart.animate(1));
+  $(document).on('click', '.js-sidebar-toggle', () => chart.animate(2));
 });