docs: add java package conventions to README.md

Author: tom-weelborg

README.md

@@ -54,4 +54,9 @@ This project is developed following the conventions listed below.
 
 ### Conventions
 
-The following are lists of conventions that either *should* be followed or *must* be followed when contributing to this project. 
+The following are lists of conventions that either *should* be followed or *must* be followed when contributing to this project. 
+
+#### Java
+
+- Packages:
+  - Names must be `snake_case`