feat: support node20 runtime (#1988)

* feat: support node20

* fix

* more fixes

* maybe final fixes?

* format

pkg/runner/testdata/actions/node20/node_modules/node-fetch/browser.js

@@ -0,0 +1,25 @@
+"use strict";
+
+// ref: https://github.com/tc39/proposal-global
+var getGlobal = function () {
+	// the only reliable means to get the global object is
+	// `Function('return this')()`
+	// However, this causes CSP violations in Chrome apps.
+	if (typeof self !== 'undefined') { return self; }
+	if (typeof window !== 'undefined') { return window; }
+	if (typeof global !== 'undefined') { return global; }
+	throw new Error('unable to locate global object');
+}
+
+var globalObject = getGlobal();
+
+module.exports = exports = globalObject.fetch;
+
+// Needed for TypeScript and Webpack.
+if (globalObject.fetch) {
+	exports.default = globalObject.fetch.bind(globalObject);
+}
+
+exports.Headers = globalObject.Headers;
+exports.Request = globalObject.Request;
+exports.Response = globalObject.Response;