Add Key Bridge shield for Maryland MDTA maintained section of Key Bridge and approaches

[talllguy]

I'd like to see this shield for Baltimore's Key Bridge (below) in Americana. It is used around the project area for recognition. Here's an approximate portion that is part of the bridge facility. I'll make a relation though.

Famartin, CC BY-SA 4.0, via Wikimedia Commons

[michaelblyons]

😭😭😭