Add a standalone example showing how to create new analysis tools

**Add a pointer to any prior users list discussion.**
https://groups.google.com/g/dynamorio-users/c/He1h6RCk-W0

**Is your feature request related to a problem? Please describe.**
We can have a small example that can be helpful in getting started when writing new analysis tools.

**Describe the solution you'd like**
A simple analyzer and the corresponding cmake setup.

Do you have any implementation in mind for this feature?

**Describe alternatives you've considered**

**Additional context**