Make boolean literal parsing case-insensitive

[althea28]

Description

Make boolean literal parsing case-insensitive to match official rosidl_adapter.

Currently, roslibrust_codegen cannot parse .msg and .action files that contain capitalized boolean literals (e.g., bool success True). This causes serde_json::from_str to panic with "expected value at line XX column XX".

The official ROS 2 Python parser (rosidl_adapter/parser.py) parses boolean constants case-insensitively by converting the string to lowercase first: if value_string.lower() not in (true_values + false_values):

Because of this, several official ROS 2 packages (such as nav2_msgs in the navigation2 stack) currently use True or False in their definitions, which compile fine in standard ROS 2 but break roslibrust's strict generation. This PR adds a .to_lowercase() call when matching "bool" in parse_ros_value.

Fixes

N/A

Checklist

• Update CHANGELOG.md (I did not update this as this change does not seem notable enough to include 😅 let me know if I should do this anyway!)