Some general documentation.

README.md

-# PROJECT_NAME
+# Example IaC project
+
+An example infrastructure-as-code project to show a simple project structure.
+
+## A note on structure
+
+This repo is first divided by the main tool used instead of by the service or
+part of the infrastructure. One reason is to document the workflow with that
+specific tool in just 1 place, not copied across different READMEs for each
+service. Another reason is that we can more easily setup our CI/CD pipeline
+trigges. For example, build a container image if files under
+`Containerfiles/<service>` have changed.
 
 ## License