Set default User-Agent to SDK/version

Author: ddumenko

src/http/http.ts

@@ -47,7 +47,9 @@ export type RequestBody = undefined | string | FormData | URLSearchParams;
  * Represents an HTTP request context
  */
 export class RequestContext {
-    private headers: { [key: string]: string } = {};
+    private headers: { [key: string]: string } = {
+        "User-Agent": "pandadoc_node_client/1.1.0",
+    };
     private body: RequestBody = undefined;
     private url: URLParse;
 
@@ -219,4 +221,4 @@ export function wrapHttpLibrary(promiseHttpLibrary: PromiseHttpLibrary): HttpLib
       return from(promiseHttpLibrary.send(request));
     }
   }
-}
+}