It's not 100% clear if OP wanted two-communication, eg. display replies as comments. His title seems to imply one-way communication only. That is super simple to implement.

Simplest solution is to use something like https://mastofeed.org/ which automatically posts your RSS feed to Mastodon.

Of course you can also do it yourself. Posting to an existing mastodon account is just a single HTTP call with an API key: https://docs.joinmastodon.org/methods/statuses/#create