Added tesla boost capabilities.

Shock troopers and tesla tanks standing near a tesla coil
will charge it up, enhancing its range, modifying the zap
animation and allowing it to work even when player's power
is down.
The sound for charger weapons edited from
https://www.freesound.org/people/JoelAudio/sounds/136542/

mods/ra/rules/structures.yaml

@@ -387,6 +387,9 @@ TSLA:
 		Footprint: _ x
 		Dimensions: 1,2
 	RequiresPower:
+		UpgradeTypes: tesla
+		UpgradeMaxEnabledLevel: 2
+		UpgradeMaxAcceptedLevel: 3
 	Selectable:
 		Bounds: 24,24,0,16
 	SelectionDecorations:
@@ -403,8 +406,17 @@ TSLA:
 		HasMinibib: Yes
 	WithChargeAnimation:
 	Armament:
+		UpgradeTypes: tesla
+		UpgradeMaxEnabledLevel: 1
+		UpgradeMaxAcceptedLevel: 3
 		Weapon: TeslaZap
 		LocalOffset: 0,0,427
+	Armament@Upgraded:
+		UpgradeTypes: tesla
+		UpgradeMinEnabledLevel: 2
+		UpgradeMaxAcceptedLevel: 3
+		Weapon: TeslaZap.Upgraded
+		LocalOffset: 0,0,427
 	AttackCharge:
 		ChargeAudio: tslachg2.aud
 		MaxCharges: 3
@@ -414,6 +426,8 @@ TSLA:
 	DetectCloaked:
 		Range: 8c0
 	ProvidesPrerequisite@buildingname:
+	Targetable:
+		TargetTypes: Ground, C4, DetonateAttack, Structure, TeslaBoost
 
 AGUN:
 	Inherits: ^Defense