Add checkout pr logic

extra/checkout-pr.js

@@ -0,0 +1,11 @@
+const childProcess = require("child_process");
+
+if (!process.env.UPTIME_KUMA_PRUPTIME_KUMA_PR) {
+    console.error("Please set a pull request number to the environment variable 'UPTIME_KUMA_PRUPTIME_KUMA_PR'");
+    process.exit(1);
+}
+
+console.log("Checkout pr");
+
+// Checkout the pr
+childProcess.spawnSync("gh", [ "pr", "checkout", process.env.UPTIME_KUMA_PR ]);