test(*): add initial tests

this is a baseline test so that `deno test` does not fail to find a test file in ci, but note that
for now this test should fail for more a few reasons which will be fixed in a subsequent commit

.github/workflows/lint-and-test.yaml

@@ -22,4 +22,4 @@ jobs:
         run: deno lint --unstable
 
       - name: Run tests
-        run: deno test --unstable
+        run: deno test --unstable --allow-read --allow-env --allow-run

test.ts

@@ -0,0 +1,11 @@
+/// <reference path="./types.d.ts" />
+
+import { assertEquals } from "https://deno.land/std@0.104.0/testing/asserts.ts";
+
+import { $ } from "./mod.ts";
+
+Deno.test("$ works", async () => {
+  const result = await $`echo hello`;
+
+  assertEquals(result.stdout, "hello\n");
+});