feat(radar): auto-zoom to cargo cannisters

Similar to auto-zooming on ships, add the capability for the radar to
auto-zoom on cargo containers. This is very useful when scooping multiple
cargo containers in an area, as otherwise the radar is liable to zoom out
to infinity in-between scooping containers. This makes it very difficult
to lock on to the next container.

TODO: the radar should be switchable between auto and manual modes, with
the manual mode being controllable by the keyboard/joystick. A radar
mode and range indicator might also be useful to add.

In future, different radar equipment could provide different ranges
and/or capabilities.

data/pigui/modules/radar.lua

@@ -122,6 +122,7 @@ local function display3DRadar(center, size)
 	local navTarget = player:GetNavTarget()
 	local maxBodyDist = 0.0
 	local maxShipDist = 0.0
+	local maxCargoDist = 0.0
 
 	radar.size = size
 	radar.zoom = currentZoomDist
@@ -136,6 +137,9 @@ local function display3DRadar(center, size)
 		-- only snap to ships if they're less than 50km away (arbitrary constant based on crime range)
 		if v.body:IsShip() and v.distance < 50000 then maxShipDist = math.max(maxShipDist, v.distance) end
 
+		-- only snap to cargo containers if they're less than 25km away (arbitrary)
+		if v.body:IsCargoContainer() and v.distance < 25000 then maxCargoDist = math.max(maxCargoDist, v.distance) end
+
 		if v.distance < currentZoomDist and v.rel_position.y < 0.0 then
 			local color = (v.body == navTarget and colors.navTarget) or (v.body == combatTarget and colors.combatTarget) or getColorFor(v)
 			drawTarget(v, scale, center, color)
@@ -165,6 +169,8 @@ local function display3DRadar(center, size)
 		maxDist = combatTarget:GetPositionRelTo(player):length() * 1.4
 	elseif maxShipDist > 0 then
 		maxDist = maxShipDist * 1.4
+	elseif maxCargoDist > 0 then
+		maxDist = maxCargoDist * 1.4
 	elseif navTarget then
 		local dist = navTarget:GetPositionRelTo(player):length()
 		maxDist = dist > MAX_RADAR_SIZE and maxBodyDist or dist * 1.4