add radar_msgs

[mojomex]

This PR adds radar_msgs.
Since all other *_msgs are excluding wasm32 I expect adding it there as well is fine. Also, I added it semi-alphabetically where it seemed to fit best. Please let me know if I should move it somewhere else 😃

[wolfv]

Thanks!

[mojomex]

@Tobias-Fischer @wolfv Thank you for the quick merge!

It seems like the package is still not available for linux-64 even though its CI passed, and the package is available for the other platforms:

pixi search --channel robostack-humble --platform linux-64 ros-humble-radar-msgs
# Using channels: robostack-humble
# Error:   × Package ros-humble-radar-msgs not found, please use a wildcard '*' in the search name for a broader result.

pixi search --channel robostack-humble --platform linux-aarch64 ros-humble-radar-msgs
# Using channels: robostack-humble
#
# ros-humble-radar-msgs-0.2.1-np126py311hbdd918e_13
# [...]

This is also reflected on the Robostack available packages table.

Thank you for your support!