Update index.ts

Author: AlexanderEpolite

src/index.ts

@@ -17,13 +17,17 @@ export class TempMail {
     private async makeRequest(url: string, post_data?: any, method?: "POST" | "GET" | "DELETE"): Promise<any> {
 
         let headers = {
-            "User-Agent": "TempMailJS/4.1.0"
+            "User-Agent": "TempMailJS/4.3.0"
         };
 
         //if the user is a TempMail Plus subscriber, add the credentials here
         if(this.api_key) {
             headers["Authorization"] = "Bearer " + this.api_key;
         }
+
+        if(method && method === "POST" && post_data) {
+            headers["Content-Type"] = "application/json";
+        }
 
         const raw = await fetch(BASE_URL + url, {
             headers,