Updated readme & Added new .msg for CAN transceiver / Simulation Interface

[colinli02]

• Added sim_cmd, boat_cmd .msg
• Updated ais_ships, added mock_ais_ships .msg
• Updated readme for above and CAN transceiver

Description

• For simulation interface PR, also updating readme to match latest specifications

Verification

• Verified using build package

[colinli02]

Do you think it is worth it to add markdown comments for formatting e.g:

1. Keep 'Type' organized alphabetically
2. 'mock' topic goes after its common counterpart

Within the markdown for future convenience?

[patrick-5546]

Do you think it is worth it to add markdown comments for formatting

Sure, good idea