Update explorer endpoints

Author: jpraynaud

mithril-explorer/pages/index.js

@@ -8,6 +8,8 @@ import styles from "../styles/Home.module.css";
 
 const available_aggregators = [
   "https://aggregator.release-preprod.api.mithril.network/aggregator",
+  "https://aggregator.pre-release-preview.api.mithril.network/aggregator",
+  "https://aggregator.testing-preview.api.mithril.network/aggregator",
   "https://aggregator.api.mithril.network/aggregator",
   "http://localhost:8080/aggregator"
 ];