refactor: Add type annotations for response objects in API request handling

src/lib/discordRateLimiter.ts

@@ -19,12 +19,16 @@ export class DiscordRateLimiter {
   public async request<T>(path: string, options: RequestInit = {}): Promise<T> {
     const url = `${this.baseUrl}${path}`;
 
-    const headers = {
+    const headers: Record<string, string> = {
       'Authorization': `Bot ${this.botToken}`,
-      'Content-Type': 'application/json',
-      ...options.headers,
+      ...(options.headers as Record<string, string>),
     };
 
+    // Only set Content-Type to application/json if body is a string and not explicitly set
+    if (typeof options.body === 'string' && !('Content-Type' in headers)) {
+      headers['Content-Type'] = 'application/json';
+    }
+
     const response = await fetch(url, { ...options, headers });
 
     if (response.status === 429) {