cmd/pkgserver: implement JS test DSL and runner

cmd/pkgserver/ui/static/run_tests.ts

@@ -0,0 +1,7 @@
+#!/usr/bin/env node
+// Many editors have terminal emulators built in, so running tests with NodeJS
+// provides faster iteration, especially for those acclimated to test-driven
+// development.
+import "./all_tests.js";
+import { run, StreamReporter } from "./test.js";
+run(new StreamReporter({ writeln: console.log }));