feat: add a license plate reader camera tool

Add find_alpr_cameras over the layer's OpenStreetMap camera extracts:
cameras in a US or Canadian area of at most 3° per side, nearest first,
with operator, manufacturer and facing direction, and the source's
attribution. Areas outside coverage or too wide are reported.

docs/CURRENT-STATE.md

@@ -12,7 +12,7 @@ Queries cover earthquakes, active fires, recent launches, aircraft (in an
 area, by identifier, tracks, and type and route lookups), ships (in an area,
 by identifier, and tracks), satellites (next
 pass over a point, and those overhead now), public cameras (including a
-camera's current image), radio stations, place search, routing, bike-share
+camera's current image), license plate reader cameras, radio stations, place search, routing, bike-share
 stations, transit vehicles, road traffic flow, weather, weather map images
 (radar, satellite, lightning), wind, the most recent satellite image of an
 area, submarine cables, regional briefs, tropical cyclones, fire