[CLEANUP] Rename Documentation/ to docs/ (#94)

This brings the project more in line with the default Symfony
project structure.

Author: oliverklee

CHANGELOG.md

@@ -12,7 +12,7 @@ This project adheres to [Semantic Versioning](https://semver.org/).
 - REST action for getting all subscribers for a list (#83)
 
 ### Changed
-- Adopt more of the default Symfony project structure (#92)
+- Adopt more of the default Symfony project structure (#92, #93, #94)
 
 ### Deprecated