Improve code quality and write tests

src/pecl.ts

@@ -0,0 +1,17 @@
+import * as hc from 'typed-rest-client/HttpClient';
+
+/**
+ * Function to check if PECL extension exists
+ *
+ * @param extension
+ */
+export async function checkPECLExtension(extension: string): Promise<boolean> {
+  const http: hc.HttpClient = new hc.HttpClient('shivammathur/php-setup', [], {
+    allowRetries: true,
+    maxRetries: 2
+  });
+  const response: hc.HttpClientResponse = await http.get(
+    'https://pecl.php.net/package/' + extension
+  );
+  return response.message.statusCode === 200;
+}