Fixed JSON method

src/llm.ts

@@ -138,9 +138,15 @@ export class LLM {
 		return Math.ceil((text.length / 4) * 1.2);
 	}
 
-	async json(message: string, options: LLMRequest) {
+	/**
+	 * Ask a question with JSON response
+	 * @param {string} message Question
+	 * @param {LLMRequest} options Configuration options and chat history
+	 * @returns {Promise<{} | {} | RegExpExecArray | null>}
+	 */
+	async json(message: string, options?: LLMRequest) {
 		let resp = await this.ask(message, {
-			system: '',
+			system: 'Respond using a JSON blob',
 			...options
 		});
 		if(!resp?.[0]?.content) return {};