spec: Implement Changelog File

[QuakeWang]

https://paimon.apache.org/docs/master/concepts/specification/

After #11 have been merged, I will start the Changelog task.

[JingsongLi]

We don't need to have changelog file now, it is for streaming read.

[Xuanwo]

We don't need to have changelog file now, it is for streaming read.

Thanks! I'll remove this issue from the 0.1 tracking list. It makes sense to further narrow the scope of 0.1 to create a usable version quickly.

[QuakeWang]

We don't need to have changelog file now, it is for streaming read.

Okay, I will start it when the streaming read is ready.