Document ground vehicle markers in README, refresh firmware.bin for v3.1.0
Adds a note to the "Hide ground vehicles" section about the new blue square markers and matching legend entry, and refreshes the root firmware.bin to match the v3.1.0 build output including the ground vehicle marker feature. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
This commit is contained in: