refactor: use gts instead of xo

feat: add browser opening to test:notification
feat: add c8 and mocha for testing
feat: update Docker and ci
style: update editorconfig

docs/javascripts/tables.js

@@ -1,6 +1,6 @@
-app.document$.subscribe(function() {
-  var tables = document.querySelectorAll("article table")
-  tables.forEach(function(table) {
-    new Tablesort(table)
-  })
-})
+app.document$.subscribe(() => {
+  const tables = document.querySelectorAll('article table');
+  tables.forEach(table => {
+    new Tablesort(table);
+  });
+});