Microsoft MakeCode

What's the best way to create a pxt target

I found the docs here: https://makecode.com/target-creation,but it’s not very helpful to be honest.
The pxt-sample is out dated and I am facing many errors when I lunch that project :disappointed:
I wonder if there is any api of the pxt framework?should I look into the source code to get what I want?
can anyone give me some advice on where to start?