Add plots for statistical significance of measurements.

* This is useful when comparing benchmark runs.
* Inspired by [Statistics for Hackers](https://youtu.be/Iq9DzN6mvYA?t=800)

Change-Id: I4f2bfdf174263e1fa1542e115c0caabcafdb53b3
Test: `npm run-script dev`
diff --git a/development/plot-benchmarks/src/lib/Chart.svelte b/development/plot-benchmarks/src/lib/Chart.svelte
index 7a063a8..9a224e2 100644
--- a/development/plot-benchmarks/src/lib/Chart.svelte
+++ b/development/plot-benchmarks/src/lib/Chart.svelte
@@ -10,6 +10,7 @@
 
   export let data: Data;
   export let chartType: ChartType = "line";
+  export let isExperimental: boolean = false;
 
   $: {
     if ($chart) {
@@ -27,7 +28,9 @@
   onMount(() => {
     const onUpdate = (chart: Chart) => {
       $chart = chart;
-      $items = chart.options.plugins.legend.labels.generateLabels(chart);
+      // Bad typings.
+      const legend = chart.options.plugins.legend as any;
+      $items = legend.labels.generateLabels(chart);
     };
     const plugins = {
       legend: {
@@ -65,7 +68,14 @@

     </button>
   </div>
-  <canvas id="chart" class="chart" bind:this={element} />
+  <canvas class="chart" bind:this={element} />
+  {#if isExperimental}
+    <footer class="slim">
+      <section class="experimental">
+        <kbd>Experimental</kbd>
+      </section>
+    </footer>
+  {/if}
 </article>
 
 {#if $items}
@@ -89,4 +99,17 @@
     border: none;
     padding: 5px;
   }
+
+  .slim {
+    margin-bottom: 0px;
+    padding: 0;
+  }
+
+  .experimental {
+    display: flex;
+    flex-direction: row;
+    flex-wrap: nowrap;
+    justify-content: center;
+    margin-bottom: 0px;
+  }
 </style>