Rate limiting support

On some confluence instances admins limits requests per second a user can send. Without that requests start failing with 
```
status=429, body:
{"message":"Rate limit exceeded."}
```
response.

Idea: add cli arg to be able to configure rate limiting.

https://github.com/ksletmoe/Bucket4k can be used along with https://ktor.io/docs/client-http-send.html