add "total score" and average score to maintainers page

app/components/total-score.hbs

@@ -0,0 +1 @@
+Total Score: {{this.score}} Average Score: {{this.averageScore}}

app/components/total-score.js

@@ -0,0 +1,24 @@
+import Component from '@glimmer/component';
+
+export default class TotalScoreComponent extends Component {
+  get score() {
+    if(!this.args.addons.length) {
+      return 0;
+    }
+
+    let score = this.args.addons.reduce((total, currentAddon) => {
+      return currentAddon.score + total;
+    }, 0);
+
+    return score.toFixed(1);
+  }
+
+  get averageScore() {
+    if (!this.score || !this.args.addons.length){
+      return 0;
+    }
+
+    let average = this.score / this.args.addons.length;
+    return average.toFixed(1);
+  }
+}

app/templates/maintainers/show.hbs

@@ -5,6 +5,7 @@
       {{this.model.name}}
     </h1>
     <p>{{pluralize-this this.model.addons.length "addon"}} maintained by {{this.model.name}}.</p>
+    <TotalScore @addons={{this.model.addons}} />
   </header>
   <AddonList @addons={{this.model.addons}} />
 </div>