Is there any tutorials for Teams online meetings bots ?

Hi everyone.

I want to develop a Microsoft Teams online meeting bot for transcribe meeting participants' voice, and show caption in real time.

I read this page, but I can not find any tutorials for developing online meeting bot.

https://docs.microsoft.com/en-us/microsoftteams/platform/bots/calls-and-meetings/calls-meetings-bots-overview

Is there any tutorials for developing Teams online meetings bots ?

And, can I use this online meeting bot with free microsoft account ?

Thank you.