change default temperature from 1.0 to 0.7

When developing prompt, it is generally better use a lower temperature
from beginning

src/chatgpt.ts

@@ -59,7 +59,7 @@ class Chat {
       tokens_margin = 1024,
       apiEndPoint = "https://api.openai.com/v1/chat/completions",
       model = "gpt-3.5-turbo",
-      temperature = 1.0,
+      temperature = 0.7,
       top_p = 1,
       presence_penalty = 0,
       frequency_penalty = 0,