fix: correct gitignore to not ignore src/amber_cli directory

- Change amber_cli to /amber_cli to only ignore root-level build artifacts
- Add missing documentation.cr file that was accidentally ignored
- Fixes CI failure where documentation.cr was not available

Author: crimson-knight

.gitignore

@@ -24,8 +24,8 @@ Thumbs.db
 !/docs/.gitkeep
 
 # Build artifacts
-amber
-amber_cli
+/amber
+/amber_cli
 /target/
 
 # Libraries don't need dependency lock