[IDEA] Add a CHANGELOG.md

**Is your feature request related to a problem? Please describe.**
We don't have an easy way to follow what have been done in the different versions of the "solution" in this repository.

**Describe the solution you'd like**
Add a **CHANGELOG.md** file based on the following example: [CHANGELOG.md](https://github.com/rpothin/PowerPlatform-ALM-With-GitHub-Template/blob/main/CHANGELOG.md)
